Google Latitude
Google Latitude is a Google service that helps you track your locations over time. You can use it like Foursquare to check-in to different places or you can use it to constantly check your location. Latitude keeps a history of your locations, which you can explore on the Latitude Dashboard. You can see where you spend the most time: at work, at home, or out and about. You can also see a visualization of your history over a specific range.