Implanted transponders for CIA agents
Disregarding the absurdity of having a young white male in such deep on the ground intel work for the C.I.A. in a Arab country, it seems to me that the CIA should have some contingency for an American CIA operatives becoming captives of a terrorist cell.
Implanted transponders of some sort would have solved the problem presented in the movie. Of course, such a program would be highly classified because of the possibility of the signal being intercepted/corrupted by terrorist cells or other countries intelligence agencies.
The technology should be available to activate it in special situations like the one in the movie and not have it transmit at all times. Ferris was holding the cell phone in the sky as a becon to his location, why not have the transponder inside him?