Google says the first customer for Google Wallet should be George Costanza from the '90s TV show "Seinfeld."

Editor’s Note: This is part of “Our Mobile Society,” CNN’s weeklong series examining how cell phones and other electronic devices have revolutionized the ways we work, play and communicate.

Story highlights

Already-useful smartphones are conquering new territory, most notably the wallet

Phones can replace your credit card, driver's license, transit pass, keys, coupons and more

The Google Wallet app went public September 19 for Nexus S smartphones

Some say phone-wallet technology is promising but must become easier to use

CNN  — 

Here’s a Googley vision for the future:

“We definitely hope one day you can walk out of the house with your phone in your hand – and nothing else,” said Marc Freed-Finnegan, the company’s product manager for Google Wallet. It aims to digitize everything in your pockets in coming years by collapsing all that paper, plastic and metal into one device: the smartphone.

The idea of using the mobile phone as a credit card, driver’s license, transit pass, digital coupon collector, house key, hotel key, corporate ID and more probably sounds pretty sci-fi-futurey. But it’s almost practical when you consider the history of the smartphone.

Since the Apple iPhone debuted in 2007 (it’s considered by most tech analysts to be the first true smartphone, running apps and functioning as a pocket computer), technologists have been cramming ever more functionality into these Swiss Army Knife-like gadgets.

Our phones have replaced many other once-common tools, from GPS devices (remember those?) to handheld gaming consoles, point-and-shoot cameras, calendars, notebooks, newspapers and portable music players.

Now they’re conquering new territory, most notably the wallet.

From there, who knows? Analysts expect phones to get so smart that they could delay your alarm clock if an airline delays your morning flight. Apple’s new “humble personal assistant,” named Siri, is a step in that direction. And technologists are working on phone prototypes that could be built into clothing, could project their screens on your skin or, in the way-off future, would have flexible and stretchable screens.

“Mobile phones are definitely becoming a center of all of our lives, I think,” Freed-Finnegan said. “When you’re carrying around this small computer, you can do all kinds of things with it.”

The phone-as-wallet trend started in South Korea and Japan about five years ago, and it’s been talked about in the U.S. for some time. But it only became a reality September 19, when the Google Wallet app went public for Nexus S smartphones on Sprint’s network. That’s a relatively small subset of people (Google wouldn’t say how many), but the company says it’s just an early implementation of what’s to come.

Here’s how it works at checkout:

Instead of pulling out a credit card to pay for your purchase, you get out your phone. Then you tap it on an NFC reader (these are becoming more common in stores and are usually labeled “PayPass” along with a little radio-wave icon) to log the payment. You have to enter a PIN for security.

Google Wallet currently works only with Citi MasterCard. Google also has a prepaid card of its own that you can load up with money from a bank or credit card account.

Some reviewers say the service is clunky.

“Other forms of payment are easier and quicker,” said Jeff Blyskal, a senior editor at Consumer Reports, who tested Google Wallet in San Francisco.

“I don’t think the Google wallet or any of these digital wallets are going to replace your leather wallet,” he said. “I just don’t think it will h