There's a whistle and a vibration in my pocket, and I pull out my phone and it's John Hodgman. He's sitting in an airport, in a Delta Airlines lounge, nursing what appears to be a whiskey on ice. He wants to talk.

Rather: He wants to answer my questions. And your questions. Anybody's questions, really. Hodgman looks bored, but what he's doing is fascinating. He's filming himself and broadcasting it live on an app called Periscope. As people ask him questions or tell him to do things, he replies to them by writing on a napkin. It's incredibly compelling, this chance to command a celebrity.

Another whistle and it's David Blaine, doing close-up magic tricks in a bar. The audience is on the other end of his phone. Another whistle and it's a friend of mine, petting his cat. My phone whistles again and now it's the investor Chris Sacca jabbering about an upcoming TV appearance. It's boring, but I sit through to the end, hoping for news. There are whistles for a kid's lacrosse game. Whistles for a violinist who plays songs on request. Whistles for an astronaut who plays guitar. Every whistle is a Periscope notification — it means someone somewhere is doing something and they want you to see it.

There is already just about everything imaginable on Periscope, which has only now hit the iOS app store: fascinating, boring, amazing stuff. It aims to be a window on the world, but an interactive window that supports not just real-time live video, but also real-time conversations around those videos.

Fire up the app, launch the camera, and the app tweets out a message (if you want it to) that you have gone live. Simultaneously, a notification fires off — with that little look-at-me whistle — to everyone following you on Periscope. As they join in, they can comment on what you're doing. And because it has super-low lag time — or latency, to use the term of art — people watching can comment on your actions more or less as they happen. It means that people watching the video can change the course of what's happening. They can chime in with questions or comments, and all the while tap-tap-tap on the screen to send a stream of hearts to the broadcaster. Don't want comments? Fine, you can turn them off. If you choose, you can let the video live on Persicope's servers afterwards, where it will stay for 24 hours before disappearing forever. Or you can choose to let your video be purely ephemeral, living only in the moment and then gone forever. It is delightfully fun.

"We want you to see the world through other people's eyes," says 26-year-old Periscope founder (one of two) Kayvon Beykpour. "It's a two-way teleportation device, and interactive enough that viewers can affect the experience." Beykpour is charming and handsome and smiles a lot for a guy who probably isn't sleeping much. The consensus that you hear about him is that he's really nice — which is something you don't always associate with someone who has already sold two companies (his first was an education-related startup) before hitting 30.

"The magic moment in Periscope is when you realize you can affect what you're seeing," he argues. "This isn't live-streaming — it's teleportation."

Teleportation?! I mean, no wonder Twitter bought Periscope for the always impressive-sounding "undisclosed sum" (it was, according to widespread rumors, somewhere in the neighborhood of $100 million). Worth every penny. It's completely fantastic.

What's more, it's a great fit for Twitter. Like Twitter, it is centered around right now. Both take advantage of the moment in public-facing ways that Facebook and Google do not. And also like Twitter, it lets you go back and catch up on what you've missed — at least for a day. It has the same asynchronous relationship aspects, where the following relationship doesn't have to be a two-way agreement. Which means that yes, it lets everyday dweebs like you and me ask questions of Genuine Famous People and get casual glimpses into their lives.

There's just one problem: Meerkat.

A notification fires and I swipe down and it is Jimmy Fallon, Meerkatting. Meerkat! The bane of Periscope, and Twitter too.

Like Periscope, Meerkat is a live-video app that lets people tweet that they've begun streaming. And as with Periscope, you can comment on people's videos as they play. Sure, there are a few hitches and caveats there. The lag time is noticeably longer in Meerkat. The video quality isn't as good. And when you make a comment on a Meerkat video, what you are actually doing is tweeting, which is a little bit of an odd interaction.

But come on, it's great, too! And what's more: It's already popular.

The app launched after Twitter had bought its prize, and quickly caught fire. It was the talk of South by Southwest, even as Twitter moved to cut it off from piggybacking on its network by taking away Meerkat's ability to import Twitter's social graph.

At SXSW there was a party at the Driskill Hotel, and there, in the front of the line, was a man in a yellow Meerkat shirt demanding to be let in, pointing at his shirt and explaining that he was the founder of Meerkat. His was the hot-shit app of South by and everyone knows it! Letting him in would clearly make any party cooler, or at least that was the implication.

"What a fucking asshole," says Ben Rubin, who is the actual founder of Meerkat and who most definitely was not the guy at the front of the line, when BuzzFeed News reaches him by telephone. And you can tell he really means it, because he won't even call out Twitter as assholes for slicing into his Achilles just before SXSW.

"I think they're very nice to us; the only thing that was weird for us was they gave us only two hours to let us know they were cutting off the graph," says Rubin. He claims he had no idea that Twitter had bought Periscope and that he was suddenly competing with a giant, publicly traded tech company instead of a few startup guys. "Nobody had a fucking clue that they had quietly bought this company. But other than this they were very nice."

Yet despite the cutoff, Meerkat was still the talk of SXSW. And reporters took to it instantly, especially tech and political reporters. The week after SXSW, White House Press Secretary Josh Earnest even sat for an interview on Meerkat. And what's more, it just raised a bunch of money. But Twitter is counting on all that not being enough.

"They have about 2–3 weeks ahead of us, and I think in the grand scheme of things the better product will win," argues Twitter's Kevin Weil, the company's vice president of product. Since he took over running product, the company has released a flurry of changes and updates. Weil exudes calm certainty when pushed about Meerkat: "We have the better product."

Rubin, however, thinks that there is room enough for everyone.

"[Periscope] is a very slick product, and very beautiful," he says. "It's very different from what we do." Rubin points out that Meerkat lets people schedule streams (so, for example, you can schedule one for 6 p.m. when it is merely 5 p.m. and let the world know about it in advance), and, unlike Periscope, it doesn't save videos by default.

But…come on, right? They're pretty similar? Rubin still thinks there is room enough for both — and more. He argues that there will eventually be four winners in different verticals — beautiful, formal, non-formal, and immediate — and makes comparisons to the way things shook out on social, where Instagram, Facebook, Snapchat, and Twitter won those respective verticals. Periscope, he says, may win the beautiful vertical, but he still has space to move in the immediate or non-formal ones.

Maybe so. But what Meerkat definitely has is a head start. The question is if it's enough. Take Instagram and Hipstamatic. Hipstamatic not only had a head start, it was an early media darling and even played prominently in an award-winning New York Times story — becoming part of the story itself. Yet today, when people think photo filtering, they think (and use) Instagram. Hipstamatic recently vacated its San Francisco headquarters, subleasing the space to another startup. Sometimes, moving first doesn't get you far enough.

This is, one would imagine, especially true if Twitter decides to really put marketing and muscle behind Periscope. While Meerkat is still seeing huge growth, according to Rubin, Twitter has the ability to put Periscope in front of hundreds of millions of people who have never even heard of Meerkat, much less installed it.

"I'm not particularly concerned about a month here or there: This is a multi-year investment for us," says Weil. "Our perspective is that live video is not just a new product, it's an entirely new category. I think it opens up entirely new behaviors, with new ways of interacting — from friends to fans to followers."

And it really, genuinely does feel like something new. Mobile live-streaming has been around for some time now, but has never really taken off — probably because it has really never worked terribly well. But a confluence of technologies has come together to make it seem truly possible now. For one: push notifications. Notifications are the most important interface element there is. They have taken center stage in the most recent versions of both Android and iOS, and as a result people are becoming increasingly comfortable with them. Add to this the camera and processor hardware, 4G networks, and operating system improvements and suddenly you understand why there has been a rush to build these personal mobile windows.

Yes, much of what we'll see there may simply be very boring, but Twitter and Facebook were both built on the backs of our banal, mundane lives. More than likely we're going to open them and see something new. Something we haven't thought of yet and cannot really even imagine until it happens. It's going to engender new actions and behaviors and methods of communicating as surely as Twitter did. Persicope or Meerkat or maybe even YouNow are going to make for entirely new ways of interacting.

Like, perhaps, interactive porn? It's something Periscope has thought of. Pornography will not be allowed, says Beykpour, but nudity will. (In other words, on Periscope, it will be presumably be OK to be naked, as long as you're not having any fun.)

But in the meantime, and until we get to those new things, there is an enormous amount of pressure to make this work. Twitter needs a hit, and Beykpour needs to prove that he can make its investment worthwhile. It's a hell of a lot for a 26-year-old.

"If you spend a lot of time thinking about how this will go, that's just not a very productive or healthy way to spend your days," says Beykpour. "I'm sure there are a lot of people who are excited and a lot of people are critical, but we're just trying not to focus on that."

And so for the past several weeks, he's just been focused on shipping. He's been focused on this moment, March 26, 2015, when he gets to introduce Periscope to the entire world. The company is suddenly feeling grown-up — it's got 10 people working full time now — and it's just moved into a new headquarters.

The building still feels pretty empty, but you can already picture it humming with people as more come on. As we walk around on a tour of the new digs, he's still unfamiliar with some of its features. On the roof, for example, there is a gas fire-pit surrounded by couches, left behind by the previous tenant, and he doesn't know if it runs on propane or natural gas. He points to a shutoff valve and explains that they don't have a key.

"They are probably universal, I could probably go buy one," he says with a shrug and a grin.

But even without it, the view from the roof is really great. It's a great building in an up-and-coming neighborhood, one of San Francisco's hottest, in fact. Yes, it's an all-round great place to be. I imagine that the last tenant — a company called Hipstamatic — must have really hated to leave all this behind.