Surely the reason such tech isn't already in place is because such communications are being recorded/monitored?
Couldn't you easily locate devices using triangulation and hand-held receivers? Indeed you could probably just have a device at the door of each cell, and in other places, that told you when a communication on the right frequency was being made.
NSA are apparently monitoring my communications and I don't have a criminal record or even live in USA ... so why wouldn't they be monitoring USA prisoners, particularly gang members?
First of all, the NSA is not omniscient. Second, the NSA is tasked with national security- ie, they don't share data with prisons even if they have a juicy scoop.
Couldn't you easily locate devices using triangulation and hand-held receivers? Indeed you could probably just have a device at the door of each cell, and in other places, that told you when a communication on the right frequency was being made.