I had an idea roughly on paper one time. Don't know how well it would have worked, but the idea was OK, at least I think.
One needs those type of footwear that has the very thick soles. I'm not up on fashion, so I don't know what they're called. Anyhow, a small motor somewhat like the stepper motor on a computer floppy drive mounted in the sole. The motor has a worm gear like shaft on it roughly a couple of inches long coming out of it. To this could be mounted bristles, or whatever fairly stiff brush like material mounted on the shaft. The batteries to power the motor is mounted in the heel. At one time you could get an infrared emmiter and receiver package from Radio Shack for a couple of bucks. This would be the control part of the device. The motor is mounted in the shoes so that the bristles just stick out where the sole of the foot would be.
The idea is that the volunteer victim wears these in public. Another person has the remote to control the motors in each shoe/boot. The remote is set up as a "momentary on" device as opposed to a "latching" one. Latching would mean that once you 'click' the remote, the device stays on till you 'click' the device again. Momentary means that as long as you hold it on, it stays on, till you release the button. This is preferable to latching because since the device is 'line of sight', if a bunch of people get between you and the victim, there's no way to turn it off till they get out of the way. That could be good or bad depending on how you want to look at it. Or depending if you have the remote or are wearing the footwear. 8c)
The idea now is that while she is out in public, maybe in a line up of people waiting for your turn to come up, the remote gets turned on, the motor starts rotating the bristles, or whatever, and they, in turn rub against the soles of the poor victim's feet. Try and keep your cool in the crowd with that happening.
Don't know if I explained that in a way to be easily understood, but that was my idea. Only on paper though as I do not have the privelige of having a willing victim to try out my warped ideas.