If you haven't seen Google's location history page, prepare to have your mind blown.

Yes, Google tracks where you are periodically. Scared yet?

Check out your location historyhere: https://maps.google.com/locationhistory/b/0/dashboard

Google Latitude

accounts.google.com

Store your past location history, view and manage it with Google Maps, and see a dashboard of interesting information, such as trips or frequently visited locations. Your location history is not shared with anyone.

See more commentary on r/Android: http://www.reddit.com/r/Android/comments/12e7rk/google_now_distance_travelled/