Here's a simple wiring diagram for using a Tilty Duo or Quad to control a self-balancing scooter. It assumes the use of a Sabertooth 2x25 motor controller and a potentiometer for steering sensing, but either can be substituted for other devices.
Please note though, that in order to read the potentiometer you need to supply it with 3.3 volts from the Tilty's servo header. This can be done by using a blob of solder to bridge the 3v3 and center pads on the bottom of the Tilty. If you use the 5v pad you may potentially damage the Tilty's microcontroller.
I plan on expanding this page when I have the time to take apart my own self-balancing scooter, so that I can better document how to hook everything up. But until then, this at least shows the connections.