Go to your local party shop. They sell all sorts of items for parties, balloons, streamers, horns, noise makes of all types. Buy one of this noise makes that you crank. There are some that make clicking sounds, some that make grinding sounds and shot out sparks. The ones that make sparks don't last very long. Get one that makes plenty of noice that fits in your pocket. Next time someone on a cell phone is driving you nuts pull out the noise maker and start cranking. Crazy thing the people on the cell phone will alway look over at me and say, "do you mind I am trying to talk". Then I reply, "Now you know how I feel." And I keep on cranking until they leave or it turns into a screaming contest and security has to deal with it.
Build yourself an EMP. It will permently kill any electronic device within 3 ft. It is totally silent all you do is push a button. Wind a pancake coil with #24 enamel coated copper wire 1/4" thick 5" diameter. Use two 7500 uf electrolitic caps in parallel 200 volts each as the capacitor bank. Use a disposible camera flast unit to charge the caps. Camera flast units are very slow on such a large cap 10 of those flash units all charging the cap at the same time is faster. Discharge the cap bank into the coil it will produce an EMP that will distroy any cell phone or IPOD within 3 ft. Be sure to paint your coil with polyurethane varnish to glue all the wire together if you want it to last.
There is lots of hostility to ill mannered people using cell phones in public places! And I thought I was unique. I totally despise mindless gabbling, where you can't escape, or the bad manners of people of all ages who seem to think their affairs (literal as well as figurative) will interest all within hearing range. They even raise their voices, so everyone can hear. How nice!
I have a friend his name is TIM. He carries a boom box with him every place he goes. He never turns it on unless there is some loud mouth jerk talking on a cell phone. Tim cranks the music up wide open the person on the cell phone usually tries to talk louder at first then they realize that is not working so they either tell TIM to turn that music off I am trying to talk or they leave. It is so funny. LOL.