In the past I built a digital switch that lets you toggle two different devices with the third channel, either intermitently or off/on toggling. It uses a $2.00 microcontroller but you need a programmer that costs a lot more.

My idea was to put a police siren and some flashing lights on my car, then run the siren and flash the lights, chasing other people's cars around the track like a maniac. Mostly just for kicks / laughs. Just an idea though. I've seen a lot of things (ie. the AUVSI show always has a lot of trucks with guns or trucks with arms, but those things require more than just an extra third channel to use with any real accuracy).