I designed a simple phone/tablet holder that snaps into a n64 controller's expansion slot. Use it with an n64 to usb adaptor and a usb to usb otg adaptor and it will control mupen64plus from the fdroid repo. Portable n64!
Later I realized the same idea would work for an original xbox controller. Basically it's the same idea as the n64 version, but xbox controllers are USB devices so they can connect to a phone without a signal converter. Just hack on a short USB cable and use a $2 USB OTG adapter. Works in cm11 and cm12 on my apexq. If you've never heard of the USB hack before, just cut the xbox cable and splice it to a USB 2 cable. The 4 wire colors should match. Leave out the yellow wire. I soldered my cable to the board, ran the wire through the original strain relief, and removed the rumble motors.