[dmoney]

Homemade vibes are a hard thing to come up with. The ones in the stores are usually powered by batteries, which are hooked up to a motor, and the motor has some type of spinning weight attached to the motor shaft. Kinetic energy ones are usually a spring with a counter-balancing weight somewhere in the middle, and the spring would cause the weight to move back and forth as you move with it in (not very good unless you're walking around with it in you). Both versions would be encased in plastic to prevent the moving parts from tearing you up inside. Both would be hard to make without a bit of mess that would be seen. Electrics usually involve soldering of components to make the connections. The kinetics are dangerous if you have the spring not set properly in the plastic, or the spring pops through the plastic. The cell phone apps are probably your best bet. The next best thing would be a small bullet vibe, an egg vibe, or a butterfly... all the smaller of the vibes.