This page describes how to build a vibrating egg that can be activated by touch. When two people touch each other, the toy will run; when they stop touching, the toy will stop.
To build this toy, you will need to find a device called a "ghost ball." This is a children's toy, available for a few dollars in many toy stores. Essentially, it's a Ping-Pong ball with a light inside it. When you pick it up, your hand touches two metal strips on the bottom, and it lights up and makes a sound.
You'll need a ghost ball, a solid-state relay, some fine wire, and the sex toy. Construction is straightforward.
First, pry open the ghost ball. Inside, you'll find a small circuit board with a little red light on it. The circuit board is held in place by the two strips of metal that act as contacts. By prying out the two strips of metal, you'll be able to remove the circuit board.
There is a small speaker in the toy, connected by wires to the circuit board. Cut the wires and discard the speaker.
Locate the LED, which is about in the center of the board. Cut it off, as high up as possible, so that the two wires are sticking up from the board.
Now solder some fine wires to the stumps of the LED leads. One of these will go to the "+" terminal on the solid-state relay; the other, to the "-" terminal. The LED has a small flat spot near one of the leads. This is the lead that must be attached to the "-" terminal on the solid-state relay.
You'll need to open up the battery pack of the toy. If you managed to get the pager open, this will be a cakewalk. If you examine the battery pack and the vibrating egg, you should see 2 wires that lead from the egg to the battery pack. One of these wires goes directly to a battery contact in the battery pack; the other wire goes to the speed control dial, which then in turn goes to the other battery contact.
What you need to do is cut that wire, and cut the wire that leads from the other contact on the battery pack. So you should have one wire that is attached to the second contact on the battery pack, and another wire which leads out to the egg.
You'll have the right wires if you can touch the stripped ends of the wires together and make the egg vibrate.
Assuming you have the right wires, these are the wires that go to the relay. Essentially, the relay is taking the place of the little speed control wheel in the battery pack; the speed control wheel should be completely bypassed.
Now you're going to take these two pieces of wire and run them to the leads marked "~" on the solid-state relay.
If you've done this right, and everything is working, when you touch the metal strips on the circuit board (the ones that used to poke out of the Ping-Pong ball), the sex toy will run.
Now for the fun part. Find two copper (or other metal) bracelets. Each one will be attached by a long piece of wire to one of the metal strips on the circuit board. Run a wire from one bracelet to one metal strip; run another wire from the other bracelet to the other metal strip.
If you want, you can put the circuit board back into the shell of the ghost ball, or you can put it in any small plastic enclosure. To use the sex toy, the user will insert the vibrating egg, and then the user and someone else will each wear one of the bracelets. When those people touch each other, skin to skin, the sex toy will run; when they stop touching, it will turn off.