They tell us where to eat, how to find friends, when to make a left turn.

Oh, and they can also make a phone call.

An explosive proliferation of software applications — and easy ways to get them, most notably through Apple’s App Store — is changing our relationship with mobile phones. The always-connected era is dawning. The cell phone is becoming more a companion than merely a means of one-on-one conversation.

“I can’t live without it,” said James London, a 19-year-old De Anza College freshman, cradling his iPhone. “It’s like water or food.”

Though Apple was the first company to create an easy and orderly way for developers to sell smart-phone software, the rest of the industry is trying to catch up.

Owners of all the major mobile phone operating systems — Research In Motion, Windows Mobile, Palm, Symbian and Google’s Android — are gearing up online application stores. Independent app sites are also popping up, offering unauthorized software for the iPhone.

Soon, nearly every imaginable function of the office and home entertainment center will be delivered to the computers that fit our palms.

“I’m a big believer that the mobile phone will become the remote control of our lives,” said Chetan Sharma, an independent wireless industry analyst. “Anything that we touch and see and feel, and whomever we communicate with — we will control that with our mobile phones.”

Though the recession is slowing sales of so-called smart-phones, futurists view app-packed mobile devices as the next tech tsunami to hit society and fundamentally change how people navigate life.

“It’s a new category of activity,” said veteran valley forecaster Paul Saffo. “Voice (functions) are an afterthought.”

Already people are using their smart-phones to locate friends at nearby bars and restaurants or find a service station with cheap gas. They stream TV to their phones, update Facebook pages on the go and play sophisticated games.

The Shazam program allows people to instantly identify a song and artist by holding the iPhone up to, say, a radio. The Trapster program for iPhone and BlackBerry uses crowd-sourcing to avoid speeding tickets — the phone signals a warning when entering ticket zones. The Android Cab4me app helps hail a cab.

‘My lifeline’

“It’s my lifeline,” said Grace Redmond, a 20-year-old San Jose State University student. “My iPhone was broken today. It ruined my day.”

Redmond, who grew up in Virginia, relies on GPS-enabled programs to help her get around, and avoid getting lost in the Bay Area. She found the Urbanspoon app indispensable during a recent vacation to Seattle. “My phone told me where to eat,” she said.

Giovanni Valasco, a 24-year-old Campbell resident, treats his iPhone like a pocket Yellow Pages by using ﻿a business listings program. “I use it all the time.”

Freshman London worries about an affliction common to BlackBerry users: sore neck. “I’m constantly looking down at my iPhone — every 10 minutes.”

Because their smart-phone is with them everywhere they go, people develop far closer attachments to the devices than to their home PCs or laptops, said B.J. Fogg, a Stanford University researcher author of “Persuasive Technology: Using Computers to Change What We Think and Do.”

Sharma said people using smart-phones spend 70 percent of their time doing things other than talking.

“They have become devices people use for productivity and leisure,” he said. “They save time and they kill time.”

Tech ‘sea change’

Last year, some 34 million smart-phones were sold in the United States, about 20 percent of the nation’s overall mobile phone market of some 173 million units, according to research firm IDC. But by 2013, it predicts nearly half the mobile phones purchased in the United States will be smart-phones.

“The sea change is starting to happen,” said IDC analyst Sean Ryan.

But there are barriers to smart-phone ubiquity. Perhaps the biggest challenge is the cost of data plans. Apple’s U.S. iPhone partner, AT&T, for instance, offers a basic data and voice plan for about $80 a month with taxes. That’s almost $1,000 a year, which can be a hard sell to the general population, particularly in tough economic times.

“The prices of service plans are big impediments for many people,” said Shaw Wu, analyst with Kaufman Brothers. “It’s not cheap.”

But service providers have a lot at stake — analyst Sharma said they pulled in $34 billion last year in data charges — and are likely to compete fiercely, which could push down costs and expand consumer options.

Hints of the future can be found at Apple’s App Store, which now offers some 27,000 iPhone applications, according to 148Apps.com, a San Francisco Web site that reviews iPhone apps. Some of those are given away for free, while many are sold for less than $3. As of mid-January, Apple said there had been 500 million downloads from the App Store, which opened in July.

“It’s like a concierge. When you have a problem, it can help solve it for you,” said Stanford’s Fogg. “Nothing is as close to us all the time — not even your spouse or partner.”

Contact John Boudreau at jboudreau@mercurynews.com or (408) 278-3496.