Grindr is a free phone app which lets gay men instantly pinpoint each other using GPS technology. It has already transformed the sex lives of 700,000 men around the world. But could it work in the straight market? And would it mean the end of monogamy?

Ever heard of Grindr? If you have, I'm going to guess that you are male and gay; or male, technically straight and somewhat curious; or the straight friend of a gay man. If not, allow me to enlighten you.

Grindr (pronounced "grinder") is a free downloadable iPhone app which, it promises, will help you "Find gay, bi, curious guys for free near you!" Grindr harnesses GPS, allowing you to establish who else in your direct vicinity is also using Grindr. It shows you – on a gridded display – who these men are and what they look like; it'll tell you how far away from you (in feet, and even more thrillingly, fractions of feet) they are standing; and it will allow you to "chat" them, if they take your fancy. Although buried deep in the Grindr ethos is the idea that you shouldn't do in cyberspace what you could be easily be doing in person. Don't "chat" when you could actually, you know, chat.

Grinding is an intoxicating experience. I was first introduced to it on the roof terrace of a bar in east London by my friends J and W. J launched the app on his iPhone and I got palpitations as the grid of portraits (ordered in terms of geographical proximity – your nearest Grindr user is posted at the top left) instantly unfurled itself across the screen. All these men, effectively coming on to – well, not me, but still… It is literally a sexy app and the overflow of that sexual potency, the decadence, sweeps you along on a wave of lust, regardless of who you are and what your gender or sexual orientation might be. I was reminded of the first time I entered words into the search criteria on Google, of the first time I downloaded music from iTunes – I knew I was engaging with a bit of technology that would alter things on a profound level.

I scrolled on and on through the grid of gay offerings, furtively trying to match the pixelated images with the real-life men ranged around me in the bar.

"But do you want to know the funny thing?" J said. "The best nights you can have on Grindr are the nights when you stay in." And he laughed, wickedly.

Grindr is reconfiguring the landscape of human relationships. Partly because it's sex in an app, the sexual equivalent of ordering take-away, or online fashion (my friend Kevin calls it "net-a-port-gay.com", and he's so pleased with himself for this he says I can use his real name. Everyone else asked to remain anonymous). Grindr was launched on 25 March 2009; now more than 700,000 (and counting) men in 162 countries around the world are using it to phenomenal effect, if J, W, Kevin and the other gay men I've asked are any kind of a guide. "I've never, ever had so much sex in my life!" R told me gleefully. "I've probably had as much in the past eight months of Grinding as I have over the 20 years since I came out. Maybe more." It's only going to get bigger, to facilitate more sex. Two thousand people download it every day, and a BlackBerry-friendly version of the app launched less than a month ago – a development which could triple Grindr's reach.

But Grindr is more significant even than that suggests. It marks a major evolution in how all of us – gay, straight, alive – will meet and interact with each other. Depending on who you talk to, this is either brilliant (liberating, socially enabling – the end, even, of loneliness and boredom); or a potential disaster (signalling the end of monogamy, facilitating sex addiction). Either way, it matters.

Arguably we are living in a post-gay era. The divide between gay and straight worlds diminishes daily. Gay culture and straight culture become increasingly intertwined. For example, Grindr's biggest boost occurred in June 2009, after gay icon Stephen Fry told the boorishly straight Jeremy Clarkson all about it during an interview on super-hetero TV show Top Gear.

So Grindr would matter even if it was not in the process of developing a straight version of its sexy self. But it is. It is likely that the Grindr experience will be open to a straight market by the end of 2010.

"Oh, at the very latest," says Joel Simkhai, the founder of Grindr. He's a wiry, neatly handsome 33-year-old man with an American accent, a hectic manner and a sharp business edge. I meet him for coffee in a chic hotel in London. This is where he's basing himself while he checks out Grindr's flourishing UK market; he usually lives in Los Angeles. "The UK is the second biggest country for Grindr after the US," he tells me. "London is the third biggest city after New York and LA. You love us."

Simkhai was born in Tel Aviv and he and his parents moved to New York ("State, not the city") when he was three. He came out in his mid-teens "just as AOL was taking off. I was born – gay-born – with online. And that was a huge help to me in terms of meeting people – people who unfortunately were a ways away in Wyoming or wherever – but still, I was meeting people who were gay and who weren't freaks." But Simkhai says he still felt isolated as a young gay teenager. He found himself asking: "The question. I think every gay man starts asking it, from the moment he realises he's gay. You are somewhere and it's: 'Who else here, right now, is gay? Who?' You are looking around, you are constantly wondering. Because coming out is a lonely process."

Still?

"Yes! Very much so! And every gay man who asks himself that question also thinks: 'Wouldn't it be good if there was some way for me to tell? Some way for me to know?' Every gay man has had the idea for Grindr."

Nearly two decades later, after Simkhai had finished a degree in international relations and economics and worked for some years in finance, Apple launched its second-generation iPhone. "It was almost as if someone was handing Grindr to me on a silver platter. The first iPhone didn't have GPS, and it only had about eight apps. They were all Apple apps, too – you couldn't develop your own. It really wasn't that great a device. But in the same announcement of the second-generation phone, they said: 'This phone will have GPS and now you can create apps!' I was like: 'Wait a minute! I know an app I want to do!'"

Did he have a complete notion of what he wanted from Grindr? How it would work, what it would look like, what sort of commotion it would create?

"Ha! No. My notion was use GPS, see who else is near. Simple as that."

In August 2008, Simkhai contacted Morten Bek Ditlevsen, an app developer based in Denmark. "He had a passion for GPS, just as I did. He's straight, but he liked the idea; he had a full-time job, but he said: 'Yeah, I'll do this as a hobby.' Didn't ask for much money."

Simkhai brought another friend, "Scott Lewallen, an expert in branding, marketing and design", into the fold. Both still work on Grindr. It took Simkhai, Bek Ditlevsen and Lewallen six months and $5,000 to build Grindr.

About the name: where did it come from?

"Nowhere specific. We liked the word. We liked the notion of a coffee grinder, mixing things together… And there's the term 'guy finder' in there, too. We wanted something that was masculine but was not about pride flags. Was not about…"

A politicised idea of gayness?

"Yes! And was fun! And was in a way – not about being gay. I'm gay; I am a proud gay man. It's not that we have any issues, right? But Grindr's not about gay rights, or gay anything. It's about finding guys. Being among your peers. Socialising. Being part of your community. It's not about: 'We're here, we're queer.'"

So Grindr launched in spring 2009. For the first few months uptake was steady but modest. Then Stephen Fry showed it to Jeremy Clarkson on Top Gear "and 40,000 men had downloaded it within a week. Amazing."

Simkhai talks with great passion about his creation. He builds a beautiful case for Grindr. He trumpets its international, unifying aspect, making it sound like the United Nations of gayness. "Here we are, 8,000 miles from home and we have 50,000 guys here in London. How? What? I haven't been here for 10 years – the first thing I did when I landed at Heathrow was launch Grindr! Sydney. Melbourne. Singapore. Tokyo! Tokyo is our fourth largest city, one of our top cities! I've never been to Japan! I don't speak Japanese!"

He points out that Grindr is a response to online dating, which causes as many problems as it solves. "With missed connections and back and forth, and: 'Oh actually, this week I'm in New York, and you're in LA…' Online dating is frustrating! It is a lot of work!" Grindr, on the other hand, is immediate. There is no messing about, no toing and froing, no building up your hopes via weeks of emails only to discover on your first physical date that you just don't fancy whoever in the flesh. You see someone's picture on Grindr, you meet immediately, you establish whether or not you're attracted to each other: "Grindr reintroduces the aspect of chemistry. And – it's real. It is not a Second Life. It is not a virtual world. It's a tool. It enables real life, it doesn't replace it."

And it leads, I say, to very real sex. None of this virtual nonsense.

Simkhai pauses.

"Er… From my perspective… it's not sex. It's a precursor to sex. It's just before. That's how I see Grindr. We want to be sexy. We think sex is part of life, the basis of life. But Grindr is sexiness rather than sex."

Simkhai is concerned, perhaps, about the conservative elements of the US media. Editorials on the danger of the "new gay hook-up app" pop up periodically. Simkhai is keen to make the point that Grindr is not uniquely concerned with procuring sex. "I meet guys all the time who say to me: 'I know it's for hooking up, but… ' But they met some really good friends. But they met their boyfriend. But. But." Simkhai says his main hope for Grindr is it will help young gay men through the process of coming out.

I am moved by Simkhai's passion, by the tales of the non-sexual impact of Grindr. I appreciate that it is still not easy to come out, and how important that sense of geographical proximity, of being part of a visible and accepting community, would be. The David Laws story breaks a fortnight after I interview Simkhai; a high-profile, sad piece of evidence that gay men still encounter problems in making their sexuality public.

Yet the men I speak to tell me Grindr is all about sex. "Internet's for dating; Grindr's for sex," D tells me. "Well, sometimes the internet's for sex, too, but Grindr: definitely sex." I ask around and am inundated with Grindr stories, all of which end in a sexual encounter. "Sometimes you don't really fancy them , but…" There's a sense of obligation to have sex anyway? "Yeah. But that's OK."

I begin to develop an idea of the culture that surrounds it. Many gay men see Grindr as a way to round off an evening. "I'd had dinner at a friend's house in west London and I was walking back to the tube; thought I'd launch Grindr, see what was going on. This guy pops up and chats me: 'You're near!' I chat back: 'I know… ' He says: 'I'm here with my boyfriend. Come and see us.' So… I did."

Others use it as you might a glass of wine at the end of a stressful day. Kev lives near a major station: "And so I get a lot of literal traffic. Men get off the train on Sunday night after a weekend somewhere stifling, probably with their parents; they launch Grindr – guess who pops up first?"

It's mixing formerly segregated elements of gay society. My 30- and 40-something gay male friends tell me they're having much more to do with younger gay men: "Which is weird, and yeah, sometimes not totally comfortable, if you think about it," says one. "You have to work out what's too young for you and stick to that limit. But – you're always honest about who you are. You've got to be. You can't say you're younger or hotter than you are; you can't post someone else's photo. If you lie you're just going to get found out, and that pisses people off, obviously. Lying isn't done on Grindr."

Cheating, on the other hand, definitely is.

"You always see on Grindr: 'Oh, I've got a boyfriend – just interested in chatting!'" says Matthew Todd, editor of gay lifestyle magazine Attitude. "Oh really? Why? Why do you need to chat to people? Why do you need to be on Grindr? Call your mum up!"

A gay man who is in a long-term relationship tells me he's aware of Grindr, but is choosing not to try it. "It would change everything. I'm very tempted, of course I am! But ultimately I don't want to go there, and I don't want my boyfriend F to go there either."

"The vast majority of guys on Grindr are in a relationship," says P. "And I reckon a quarter of the guys who use it are straight. Not curious or bi or whatever. Straight."

"The straight ones are all talk!" says D. "They love the idea that sex with a stranger could be that easy, could be downloaded on their phone… But when it comes to it, they won't do anything."

Not every gay man is enamoured of Grindr. Attitude's Matthew Todd has reservations. "A friend with an iPhone showed me it about a year ago and said: 'Can you believe it?' I rolled my eyes and thought: 'There is no way of stopping this.' Find any new technology – we will always bring it back to sex." Todd's used it ("I dip in and out") and he knows from feedback that Attitude's readers are using it a great deal. "I think it's good for people to be able to connect. Especially young people. It's good to be able to see that there are other gay people around, and to be able to interact. But at the same time I think it's a very adult world. The commercial gay world – which Grindr is part of – is a very adult, very sexual world. And I worry when I see these young kids coming out on to the gay scene, and everything is about sex. There's no real concept of relationships."

Others condemn it more directly. "Grindr's addictive," writes one man – the ex-boyfriend of a close friend – by email. "Grindr and Gaydar [the UK's biggest gay dating site]… A lot of gay men have addiction issues. I feel crap even writing it, but there it is. We drink, we use drugs and we use sex to overcome the shame we feel. And we feel worse because we know we shouldn't feel shame, we should feel pride – so we abuse drugs and sex more. Things like Grindr and Gaydar enable that sort of sex, sex which is compulsive and which dehumanises you; and means you in turn dehumanise the people you are having sex with." He puts me in touch with G, a man he met while seeking treatment for sex addiction. "I've lost entire weekends to sex," writes G. "Downloading porn, going on Grindr, meeting men whose names I don't find out, having sex; downloading more porn…"

"Low self-esteem," says Todd. "I see it a lot in gay men – it's inevitable after years of repression and shame. And what's better for self-esteem than someone having sex with you?"

Could Grindr work for a straight market? There is, I think, an undeniable gender divide on the things that men and women will do for sex, and the things they expect and want from sex. Yes, women are capable of having inconsequential flings. We are capable of one-night stands. We are capable of having sex without becoming emotionally involved. FitFinder – which allowed undergraduate users to post descriptions of people they'd seen and fancied on their university-dedicated website – became extremely popular earlier this spring, before university authorities banned it, which would suggest that there is a straight market for a location-specific dating concept. But I'm not sure Grindr could fully accommodate the complexities of male-female interactions. The gender politics, the power games, the ebb and flow of interest, the tedious but totally authentic need most men feel to pursue a potential sexual conquest…

I ask a handful of straight women – some single, some not – if they think they might be interested in a Grindr equivalent; they say they can just about envisage it working, although none of them would commit to the notion of using it themselves. The straight men I poll say they'd think less of any woman who "advertised herself like that" – and then all insisted on downloading gay Grindr on to their phones, "just to see how it works".

If anyone can make and sell a straight Grindr, Simkhai can. He does concede: "I'm a gay man and I know how to think like a gay man… actually, my sense is I know how to think like a man. I'm not a woman. I don't know how to think like a woman." Yet he says he gets more requests for a straight Grindr from women than he does from straight men. "Many more. Which might be because straight women are often friends with gay men, so know about Grindr… But I do think it would be relevant for women. I do." Furthermore: "We'll redesign it; we'll call it something different, market it differently. We have to. Gay men are very territorial. They want to keep it all to themselves, but they say: 'If you have to make a straight version, call it something else. Grindr is ours.'"

I am still sceptical, but then Simkhai says: "This notion of: 'Who is around me? Who is in this room now? Who else is like me?' – this is not just a gay thing. And this thing where: 'I want a more fulfilling life. A richer life!' This is not just a gay thing either. Gay men don't have the monopoly on loneliness and isolation." He is right, of course. As I say goodbye to Joel Simkhai, I find myself thinking: however straight Grindr plays out for us – even if it opens up a Pandora's box on our sexuality, alters forever the way men and women relate, leaves us vulnerable to a whole new world of emotional and sexual complications – bring it on. It's going to make life more interesting.

grindr.com