Everyone knows the accelerometers and sensors that are compatibles to the nxt, but in this case gdoset has done a similar device but full mechanical, with an XL motor as counterweight and the PF remote control.
Simple, smart and funny way to control RC sets and mocs!
As he say in Youtube:
"Control your LEGO creations with a motion sensor that functions like a single axis accelerometer, making it' steering feels just like Nintendo Wii."