I've only just bought the plans for the ghost in the machine, but have been thinking it through for a while now. Bought the stuff today and came to about £15 with me buying more expensive extras than were strictly needed.
plans here
http://www.lebanoncircle.co.uk/Compendium_Page.htm
The lebanon ghost in the machine is just a buzzer that can be on or off. But a lot can be developed through simple code systems. Yes/no answers, numbers, etc. Think of basic ideas like spirit bells or tambourines when used in the detection of spirit. I reckon something very basic can still create the right hebejebes. The whole idea of less is more. The witchboard looks like it does a lot more, but it should be for the price. If you really wanted to you could take the mechanism of the ghost in the machine and make your own more complicated set-up with different lights for different answers.
Anyway the plans for it are in the compendium. It also has plans for being able to make setups for a pk ouija board and for making electrical devices that can go on and off without being touched. Just gives the basic idea for a torch, but could be done on other basic electrical items without needing too much of an electrical knowledge. A few other plans for effects that may be suitable for that sort of performance.
Themagicwand did make one. Thread listed below.
http://www.talkmagic.co.uk/ftopic26764.php