Yeah, I was wondering why you couldn't just use a bridge pickup, usually used on acoustic guitars and use piezoelectic sensors.
However you will need active electronics, probably in the guitar, to do anything with it. Driving the regular pickup coil to have any effect on the strings (I'm assuming you are not using this as a pickup, but rather trying to couple the signal back to the strings using it) will require an amplifier and driver, but I doubt that it will be worth the hassle. Just rub the strings against the drummer's cymbal with the amp cranked up, it will drive everyone crazy!