Today Google launched a free new application called Latitude, which shows you the real-time location of your friends on a map—as long as they've agreed to broadcast their location with you via their cell phone.
If you volunteer to use the service, which you can shut off at any time, you allow your phone to use GPS satellites and cell-phone tower triangulation to determine your location and broadcast it to the people you select. Your cell phone's location can be determined within roughly 10 to 500 meters, depending on factors such as whether you're indoors or in a rural area.
The service works in 27 countries and can be downloaded to your phone at google.com/latitude. It works on most color-screen BlackBerries, most phones with Windows Mobile 5.0 or later, most Nokia smartphones, and T-Mobile G1 phones. A version for iPhone and iPod Touch users is coming shortly. See a video explaining the service below.
Google's Latitude is part of a trend in location-aware applications for cell phones. Journalist Mat Honan recently tested a bunch of these applications for Wired ("I Am Here"). Here are a few he liked most for travelers:
Displays Wikipedia entries about local points of interest you're passing in front of. ("Did you know that San Francisco's Marina District exists largely because a land speculator built a seawall in the 1890s?")
Posts gas station locations with current prices, so you can find the best deal.
"Kicks in when you enter certain zones," letting you automatically set your ringer to go silent when you arrive at work, a movie theater, or your hotel room.
Other applications for cell-phones of note are:
Cab4me which helps you find a cab based on your location.
Are there any apps that you recommend? Post a comment below.
And here's a video of Google's Latitude app: