Oooh - pretty blue light! http://www.griffintechnology.com/products/powermate/index.html And it can be used for other stuff - essentially it's just a big aluminum jog dial - but it looks so cool!
Yep, I've got one. It's GREAT for games when I'm using headphones. Once I get my new case built, I plan to find a way to mod it into the case. I just need money so that I can get my water cooling stuff and then can get the case planned out just right so that I can get it cut and build it. Plexi baby! My main problem is figuring out how I'm going to mount the drives. I've no clue where to it or to find the screws that will fit into the drives and still be deep enough to penetrate the plastic too. In all honesty, I really should rip the drive cage out of another case. But that doesn't look as good. Especially since I want to window mod my CDROM and/or HD.
As just a volume control knob, it seems a bit of a waste to go through all the hassle of of USB. As a multifunction device, the price isn't that bad. One could be built for around 30$US. The only problem would be the software.
Oh yeah, unless they've updated the pics on the site, the thing looks WAY cooler in person than in those pics. Nope, just checked. They haven't. One of those would go really well with one of the lighted mousepads too. Especially if you did the mousepad with blue LEDs.