If you use an Android phone with location services turned on Google is tracking your location.  Want to see where you have been?  Just go to https://maps.google.com/locationhistory/b/0 and log in with the same account that you use on your phone.  The map will show you where you have been for the last day, week, or even month.  Now, this works best if you travel long distances or in areas with a lot of cellular phone towers, but should show up some general locations even if your travels are minimal.  Is this amazing, scary, or some of both?