Reality Mining: Discovering your relative location
Look at the compass above. With a mobile device, it should rotate and point towards North.
As an example you could see that the user is sitting at the desk in the office and maybe it’s Saturday. Now you could serve an Ad about making holidays or maybe promote his/her favorite pizza ;)
Or maybe the users device is in a tilt position for reading and the direction seems to match the direction from every evening. So the user is probably sitting in front of the tv (maybe it’s late at night) and so you could serve an Ad to guide him/her to a special movie to rent online.