No wires on a GPS dude. You just buy one and they are lithium charged in your house... Then you buy a motorcycle GPS mount and rock it...
They are fairly cheap, no where near as cheap as a speedo, but the plus side is they are accurate, can tell you exactly where you are and get you anywhere, and you can use them in your car, on your bike, walking, or whatever...
You pay the price for the unit up front, then a monthly charge for the service... It's cheap.