Along that same line.....
howzabout a radio transmitter that, when aimed at a car with one of "boom cars" with the subwoofers that you can feel before you hear it, will send a tightly-focused directional signal of high-powered
(and I'm talking megawatts here!) radio "hash" that will immediately overwhelm the vehicle's radio or CD player, causing the speakers to emit feedback, static, or some other form of electronic garbage annoying enough that the operator of the vehicle turns off the system.
Nothing permanent, nothing harmful; just something to make 'em shut up and go away.
-"BB"-