I hearded about joystick-like device that can be controlled with your feet. Never tried that, but it could solve wasd movement controls for your friend and other actions can be surely mapped on something like Razr Naga.

I couldn't google any of this device, but I saw one in university lab. It was circular board - much larger than usual pedal-size with 4 springs at edges. It may be possible that it was custom built though.