I've fantasized for years about having something in my car that I could not just interrupt cell phone signals, but burn the things up completely. Pass one of those idiots, press a button and see smoke coming from his/her phone.. But, alas, then the FCC would be looking for me like they did back in the old CB days and people running high wattage amps. Hey, maybe something like 400watt amp through an old CB? Hmmmm? They were notorious for throwing out a very 'dirty' signal. I had a guy yell at me at a stop light saying my CB transmission was coming through his car radio, and his radio wasn't even turned on.
I remember one night I was parked in front of a drug store while my wife ran in for something. I was talking on my CB, (250 watt amp) and she came running out saying she could hear every word I was saying over the store's PA system. Might work on a cell phone.

Tom