"One of the most popular ideas was for Latitude to keep track of location history, allowing you (but not your friends) to see where you've been at any point in time. Another popular idea was to notify you when you're near your Latitude friends so you can easily meet up or grab lunch."

Selective Alerts

Location History enables a user to review where he or she has been, and it can be seen on Google Earth, Google Maps, or played back on the user's device. Location Alerts, which is in beta form, provides friends with updates on a user's comings and goings.

Lambert's posting said Location Alerts only works in conjunction with Location History. This way, once the system is "trained" -- which takes about a week -- text-message alerts are not issued if the person is carrying on business as usual. So only going to a strange location or a familiar location at odd times will trigger an alert.

Tina Teng, the senior analyst for wireless communications for iSuppli, said the new Latitude features face some challenges. The first is how widely distributed Gmail is, since the e-mail program is needed to use Latitude on a desktop PC or a laptop. "So there is a community issue," Teng said.

Security is Paramount

Perhaps even more serious are issues of privacy and security in an era in which people are concerned about stalking and other potentially problematic uses of tracking technology. Teng said some people don't want their precise location to be tracked, and even pointed to similar services that allow bogus locations to be offered.

"It all depends on the personal level of comfort," she said of the odds that the service succeeds. "If you are tracking people, there always are going to be security issues, safety issues. The good thing about Google Latitude is the user can decide what they want people to see."

Teng sees enterprise uses for the new service, which so far is aimed squarely at consumers. At first, business uses likely will be rudimentary. For instance, Teng said, refreshment trucks are increasingly common in New York City and Los Angeles. The new Latitude features could be used to track them, she said. "I can see food vendors putting their location on Google Latitude and History so people will know when they are in the area."

She said Google is doing the right thing in continually introducing new applications and constantly reusing the information that it gathers.