iPod touch, app for speed measurement?

[Savage-Flux]

is there an app for getting the speed of my flux? im goin down to the end of springfield road to go bashing by the gravel pits, and it has a big long road, and I wanted to know, if I jam my ipod into the reciever box, will it recodr speed? and can speed be in any way, related to G-forces, cause there is a dynamometer app. just dont know if it's the right one. anyone ever done this before?, I have the 64GB iPod touch 3rd Gen.