I wonder, how hard would it be to start slipping modified cell phones into the local cell phone supply in a place like Afghanistan. Perhaps rigged so they have small internal batteries (in addition to the detachable one), and occasionally turn them selves on and send out a GPS signal without indicating any sign of being turned on to the user.
Or maybe another option would be for the cell phone to have an internal clock, and if it's turned on after it's been left turned off for a long time it sends a GPS signal the moment it is activated. Most normal people don't buy a cell phone and then leave it turned off for months on end. (Some do, of course, just not most people.)
The basic idea is that, if some types of erratic behavior cause a cell phone to transmit GPS information, then we would not only know when people are behaving erratically, but we'd also know where they are when they do it.