One I could think of is you could use accelerometer data to know if the phone is moving, and how: is it just being lifted and interacted with, is the user walking or running, are they in a car.
For a high profile target you might also be able to track their approximate location if you know their starting point and their acceleration profile - speed up, slow down, turns, time taken. Enough, at least, to execute an ambush.
With enough data and a high SNR, you don't even need the starting point or the velocity profile. Just the turns and distances are enough in combination with a map to uniquely identify most journeys. The problem with applying that more globally is sensor drift.
