Like Foursquare or Facebook's check-in service, Latitude allows mobile phone users to check into locations or broadcast messages that include their location. But Latitude has an added twist.
According to Google, the most commonly cell phone text message is some variant of "where are you?" Latitude aims to solve that problem by literally showing where your friends are on a map -- and it will show your friends where you are on a map too.
Aware of the privacy concerns associated with location, Google designed Latitude so that people need to accept friends' invitations to see where they are -- location data isn't automatically disseminated to a person's contacts.
