The feature, dubbed "Latitude," expands upon a tool introduced in 2007 to allow mobile phone users to check their own location on a Google map with the press of a button.
"This adds a social flavor to Google maps and makes it more fun," said Steve Lee, a Google product manager.
It could also raise privacy concerns, but Google is doing its best to avoid a backlash by requiring each user to manually turn on the tracking software and making it easy to turn off or limit access to the service.
Google also is promising not to retain any information about its users' movements. Only the last location picked up by the tracking service will be stored on Google's computers, Lee said.
The software plots a user's location - marked by a personal picture on Google's map - by relying on cell phone towers, global positioning systems or a Wi-Fi connection to deduce their location.
The system can follow people's travels in the United States and 26 other countries.
It's left up to each user to decide who can monitor their location.
The social mapping approach is similar to a service already offered by Loopt Inc., a 3-year-old company located near Google's Mountain View headquarters.
Loopt's service is compatible with more than 100 types of mobile phones.
To start out, Google Latitude will work on Research In Motion Ltd.'s BlackBerry and devices running on Symbian software or Microsoft Corp.'s Windows Mobile. It will also operate on some T-Mobile phones running on Google's Android software and eventually will work on Apple Inc.'s iPhone and iTouch.
To widen the software's appeal, Google is offering a version that can be installed on personal computers as well.
The PC access is designed for people who don't have a mobile phone but still may want to keep tabs on their children or someone else special, Lee said. People using the PC version can also be watched if they are connected to the Internet through Wi-Fi.
Google can plot a person's location within a few yards if it's using GPS, or might be off by several miles if it's relying on transmission from cell phone towers. People who don't want to be precise about their whereabouts can choose to display just the city instead of a specific neighborhood.
There are no current plans to sell any advertising alongside Google's tracking service, although analysts believe knowing a person's location eventually will unleash new marketing opportunities. Google has been investing heavily in the mobile market during the past two years in an attempt to make its services more useful to people when they're away from their office or home computers.
Google shares rose $2.55 to $343 Wednesday.
NEW YORK AND TRI-STATE AREA NEWS
SEND TIP OR PHOTO || REPORT TYPO || GET WIDGET
EYEWITNESS TWITTER || FIND US ON FACEBOOK