Ever need to know where your friends are at all times? If you find it important to stalk your friends’ whereabouts, Google Latitude is for you.

Launched today, the new app for Google’s Mobile Maps pinpoints your friends on a mobile map. For mobile marketers, this may provide a fine opportunity to pitch two friends a coupon for a local meetup… if friendly mobile stalking takes off.

Granted, this opt-in program isn’t designed for everyone. To protect privacy, Google specifically requires people to sign up for the service. People can share their precise location, the city they’re in, or nothing at all.

Google hopes its mapping technology will lead to big ad dollars, of course. Google Earth, with its coverage of the globe, could make money – one day. “The near-term opportunity is in local search,” for example people looking for restaurants or hotels, said John Hanke, director of Google Earth and Maps, in an interview with CNET. Google has begun experimenting with advertisements on Google Maps and Google Earth, added Peter Birch, product manager of Google Earth, at the launch event.