Who jams these days? I do, for one
When I visited ShenZhen, China's electronics workshop in GuangDong Province I picked up a cell phone/GPS jammer that is disguised in a cell phone case and aa higher powered one I use on my motorcycle and SUV.
Never has eating in restaurants and riding on public transport been so peaceful, as well as the odd occasion I take in a movie. No more "I'm passing the (whatever)" or "How's the weather" yelled by some idiot who hasn't a clue how to use a volume control or modulate their voice (talking quieter usually causes the other party to speak louder.
The larger unit has settings to force handsets into vibrate/ringer off, as well as wideband jamming with frequency selection. Best $168 I have spent for a long time.