Sounds like it is just a matter of time before a large percentage of the population in high density areas have these things since prices will most likely fall as demand picks up. Now if they could design a zapper to change the volume level on boom boxes.
Portable Cellular Jammer
Looks just like your mobile phone, allows you to carry it anywhere without others aware: in class, in seminar, in shop, place of worship, library, on train or bus during trip, etc.