Mark Lennihan, Associated Press
The G1 is the first cell phone to use Google's mobile software.

NEW YORK — The first cell phone running Google Inc.'s mobile software looks something like Apple Inc.'s iPhone and has a large touch screen, but it also packs a trackball, a slide-out keyboard and easy access to Google's e-mail and mapping programs.

Google made its debut as a cell phone software provider Tuesday at an event where wireless carrier T-Mobile said it will begin selling the G1 phone for $179 with a two-year contract. The device hits U.S. stores Oct. 22 and heads to Britain in November and other European countries early next year.

The phone will be sold in T-Mobile stores only in the U.S. cities where the company has rolled out its faster, third-generation wireless data network. By launch, that will be 21 cities, including New York, Los Angeles, Houston and Miami.

In other areas, people can purchase the phone from T-Mobile's Web site. The phone does work on T-Mobile's slower data network, but it's optimized for the faster networks. It can also connect at Wi-Fi hotspots.

The data plan for the phone will cost $25 per month on top of the calling service, at the low end of the range for data plans at U.S. wireless carriers. And at $179, the G1 is $20 less than the least expensive iPhone in the U.S.

Sergey Brin and Larry Page, Google's founders, made a surprise appearance at the launch event. "It's just very exciting for me as a computer geek to be able to have a phone that I can play with and modify and innovate upon just like I have with computers in the past," Brin said.

He said he'd written an application for Android already: When a user throws the phone into the air, the program records how long it takes until it lands, using the phone's built-in motion sensor. Brin acknowledged that the wisdom of including such a program with an expensive phone is dubious.

"We did not include that one by default," he said.

Page said the mobile phone industry, which sells 1 billion units a year worldwide, was a tremendous opportunity for Google.

Google is giving away Android, the software that underlies the G1, for free, and opening the operating system to third-party developers who can create their own programs. Google hopes that in turn, mobile phones will provide even more ways for people to interact with the company's advertising network.