I have always enjoyed taking apart electronics to salvage components and see what makes em tick, and this is a little mod that let me dig into the guts of a relatively straight-forward device: an XBox controller. I have a bunch of old controllers around, along with some Arduino Nano boards, so decided to join another together with an RF module in order to control various devices wirelessly. The controller basically consists of a bunch of potentiometers and buttons arranged in an easy-to-operate kind of way, so this build is fairly simple in theory. As such, the wiring is fairly straight forward, there are just a lot of wires to connect to make use all of the inputs. I chose an APC220 radio module due to its ease of use (UART/TTL), range (1Km), and the fact that it allows communication with computers and Arduino based devices. The settings (frequency, data rate, etc) can also be changed on the fly, so it is fairly versatile. Any Arduino compatible RF module could be used in its place. I believe this would work similarly with a 360 controller, but haven't taken one apart... yet.
Not sure if you knew this already, but those controllers actually use USB. Microsoft just made the connector proprietary, you can cut it off and solder on a normal USB connector.
Cool project, I also have a cabinet full of those old controllers.
I knew about the USB connection, and was initially looking at the possibility of using a USB host shield to read the data from the controller, but couldn't seem to find any examples or info on whether the Orig. Xbox controllers are supported. The general size of the shields and the extra cost involved were also a factor. 360 controllers seem to be supported, but I'm still unsure about these, so if somebody could clarify, please feel free.