
[whatsisface] sent in his scratch built clone of a Griffin PowerMate. The PowerMate... is just a big knob, so it's easy to why more than one person has attempted this. [whatsisface] was inspired by a bit-tech post that did nearly the same thing, only they used the head out of a VCR for the knob. All the other components, like the optical encoder, are salvaged from a mouse, which we talked about in our scavenging How-To. He used a RC car tire for the actual knob. While we're sure it works great in dirt, we'd probably go with the weight and inertia of the VCR head instead. Have a look at the video below to see the knob being used with the Volumouse software.
http://www.hackaday.com/2008/08/17/scratch-built-jog-wheel/