The Steelcase Walkstation is the beastly life form created when your cubicle desk gets drunk at an office party, stumbles into a gym and bangs a treadmill. They'll be available soon for around $6,500, which doesn't include the computer. Making it way cheaper to mod a desk and treadmill yourself. I'm going to have to pass. Masturbating to internet porn is hard enough with my miniscule penis, I can't imagine trying to do it at a jog.
Steelcase's Walkstation marries desk and treadmill [engadget, thanks to the very fit Tara for the tip]