Google is supposedly launching a program called “Latitude” later today that allows mobile phone users to know exactly each other are at all times. In order to protect privacy, the company specifically requires people to sign up for the service.

"What Google Latitude does is allow you to share that location with friends and family members, and likewise be able to see friends and family members' locations," said Steve Lee, product manager for Google Latitude. For example, a girlfriend could use it to see if her boyfriend has arrived at a restaurant and, if not, how far away he is.