I think I'm confusing it with something else then. My friend has this gadget (not sure if microsoft even allows it) that lets you use a mouse and keyboard to play xbox.
Yeah, it's different. That link is a PS2 controller rebuilt into a design where you can control it with one hand and an insane claw grip, and an adapter for Xbox 360. I've seen those remapper things. They're definitely considered cheating, but obviously there's no way for anyone to know unless you tell them, as it just looks like a normal wired controller's input. It would come in handy for lots of other stuff too. Definitely a sweet purchase.
People who have lost mobility in one hand permanently will generally have more developed motor skills in the remaining hand so using a one handed controller isn't too difficult. It would be cool to learn and would work for forging though.