Help: music input vibrate output

I need help designing or even just putting together something for an interresting project. My sibling is making a dress for part of her masters which requires to have a music (via ipod, of course) input, and requires a vibrating output to pulse to low frequencies.
I have found a couple "vibrator" items that might work, but are a little costly, considering a large number of them are required.
I am wondering if someone has some input; is there something already that exists that i could piece together, or get some help designing from the ground up?

Basically just need a music input with vibration on the low frequencies for output. The easier thing i can thing of weighs about 30kg involving battery, cross over, amp, and some small vibrating motors (I'm a car audio kind of guy). She says that's too much

Thanks for the help

Do u need like a vibrato units used in musical instruments? if u do u might want to search for guitar vibrato like this one **broken link removed** . u may have to put a filter over there if u want only low freq to vibrate. Basicly u need a VCA, a filter and an oscilator to drive the vca. If this is what u want i can give u more schematics on guitar vibrato units.
But the simplest solution as i see it, if its not live music then use a computer software (like adobe audition) to generate the effect u want and then save it to ur ipod and play it.