Reality Mining: Are you lying in your bed right now?
So we get all kind of data like the tilt of the device. We could use this to determine if the user holds the device in its hands (shaking movements), has the device on a table (no shakings) or is lying on their back (device almost perpendicular). Now combine this with the ambient light sensor and you know precisely that the lights are off.
Now that I know that you’re lying in your bed and it is dark, I could check the device direction… If your device doesn’t point in the same direction as nights before, you’re probably not lying in your own bed right now… ;)