I have a handheld cell phone jammer that I ONLY use when I go to restaurants.
It will do a continuous jam for 800 Mhz and 1900Mhz and will jam TDMA,AMPS,CDMA,NTACS,PCS,DCS,GSM,NEXTEL,Direct Connect for a
30 foot diameter around me.One of the best toys I own..
BUT
it is illegal to own in the USA.
There is one with enough power to jam the cell phone in the car next to you BUT that is a much bigger risk to own and you could accidently jam somebody making an emergency tel call.!!