I used a http://www.saleae.com
logic analyzer to decode the output from a Logitech wireless PS2 controller.
The logitech controller comes with the controller and the receiver/transmitter unit that plugs into the PS2. I cut a wired controller cable, and spliced it to a lynxmotion PS2 adaptor cable (PS2 to header), in which I plugged the RX/TX module. I used the Saleae analyzer to look at the signals at the splice. After months (!) of trying to decode the signal, I realized that the signal is just SPI and I decoded it in one afternoon. (actually it was my friend Matt who said, "that sounds a lot like SPI, dude." FUFME.
Anyways, see the spreadsheets here:http://spreadsheets.google.com/pub?key= ... utput=html
Easily add wireless to you project now! lots of chips have SPI modules built in, so you should be able to add this to your system easily. (The cable I got from lynxmotion makes it easy to plug in the RX/TX module. )