GPS tracking, for one.
Not really.. On my phone I can turn GPS tracking off or on as I see fit.
Tracphone and other prepaid provider do offer phones with builtin E911/GPS.
All cell phones are able to be located once they are used, if you know which one you are looking for. Triangulating their position via cell towers has been done for a number of years. No GPS device need be implemented in the phone.
The main problem is the anonmity of the caller. Since they are bought for cash, there is no connection with the person who bought it.
Personally, I am not sure these would be AQ types buying these phones. The 9-11 guys followed the rules and didn't care if you knew who they were AFTER 9-11. I believe the same would be true here, unless the AQ types are running out of dupes willing to suicide for the 'cause'. I would more readily believe these phones are for people that want to use them and toss em. Drug dealers and gang members. Only problem with that thought is... I am not sure how many drug dealers or gang members are ME descent.
So I guess we are back to AQ.