I think rolling mass callings of all cell numbers periodically would keep Islamo's on their toes...if they happened to be assembling their little "toys" and a call went thru at the wrong time....kablooey! We would find out real qickly where various terrorist cells "HAD BEEN"!(snickers)!
I like your suggestion a lot!
All that will make the bad guys do is switch to programmable cell phones or PDAs with wireless or cell support. This would allow them to validate the activation codes.
Such systems are already used from power cycling equiptment and other legal uses.