In the manual to Guitar Hero II it says that the port at the bottom of the guitar is for a pedal. I believe it is to control Star Power and Whammy Bar. Seems that PS2 version had one but no sign for XBox 360. Can one be bought for the 360 or maybe built to use this facility. I would like to try building one to use the built in port but can't even find any plans anywhere.
I don't specifically know or have not been able to find anything yet either. It would be my guess that between all of the releases and competition to get games to the market that this has not been developed yet. Between GHWT, DLC content, Metallica and the revenue these items would create versus a small addition to the game just would not be on the priority list. Just my guess