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 will be able to buy 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.

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.