Enter the Punch-Out!! compatible Slam Man, the boxing dummy designed for a workout that's been modified in the DIY way to work with an NES emulator. In theory, a cool concept, one that would have potentially interested me in looking for free Slam Mans on Craigslist. In reality however, it's a little less elegant than one might think, as the Slam Man has been modified with actual arcade buttons and switches for each control input that Little Mac is capable of.
The theory version may not be possible. But I'm guessing that there's some enterprising third party peripheral maker willing to throw its hat in the ring. Anyone? Mad Catz? Hello?