You can hook it to your encoder (ipac, kb hack, joy hack, whatever) the same way you hook up any other joystickwith microswitches. But you need to supply 5v power to it. This 5 volts can come from the Ipac if you have the ipac wired for it. It can come from a hard drive connector, I believe 5v is the red wire and the yellow wire is 12v but double check that before you believe me or you can get a 5 volt transformer to power it.
They are super simple to hook up, I wish I had the money to give them a try because they sound pretty sweet.