I'll pass on any ideas that might be of interest.
In fact, for the tickling in public crowd, how's this idea I had a few years ago? Again, this would need someone to try this out on to fine tune it.
Again, using my other pastime of hobby electronics, another warped idea I've had pop into my mind is the following;
In my assortment of electronic goodies, I have some very small motors that were salvaged from dead floppy drives, etc. Some have small worm gears as a shaft that extend from the motor body anywhere from 1 to 2 inches in length. As well, on the surplus market are small IR transmitter/receiver packages for the tinkerer. These 2 items, along with a few discrete components, make up the bulk of my device. The only other needed item is the help of someone who is familiar with shoe or boot repair.
Here's the idea. We need a pair of shoes or boots that have those real thick soles on them. (not sure what they're called) We need those for the space required to fit the receiver control and the motor end of the tickle device. The motor has small brush bristles, or any type of fairly stiff fibers that would cause tickling discomfort on the soles, attached to the worm gear shaft. The motor is part of a circuit that is placed in a hole cut into the base(sole) of the boot, and is activated by the transmitter portion of the IR device. The only part that would stick up into the actual foot area are these bristles. The transmitter is small enough to be hand held by the one in control. The device can be activated 2 ways. Latching or momentary. Momentary is the safest because this all has to be done by line-of-site. In other words, the transmitter has to have a direct path to the receiver to work. Momentary means that as long as you hold a transmit button down, the motor operates. Take your finger off and it stops. Latching means that when you press the transmit button once, it goes on, and stays on till pressed again. If this latched on and something got between the transmitter and receiver, there would be no way to shut it off.
The idea is to have a willing victim put the footware on and go out on the town with the one in control of the transmitter. Wait till the victim is in a public place, especially in a lineup somewhere and hit the button to turn on the motor and start those bristles rotating and brushing against her soles. Then sit back and watch what the victim goes through. Could provide some interesting entertainment.
Like all other R & D projects, it would take a bit of experimenting to get it right. But I think could be worth the time. Anyway, like before, critiques, good, bad or indifferent are welcome.