I thought this was a great idea, but it was not really quite the playable experience I was looking for. I wanted something I could actually play as if I was punching the person I was playing. This led me to modifying my Slam Man Boxing Dummy to add arcade buttons I could punch.
Step 1: Unattach Foam
Step 2: The Back of the Head
Step 3: Wire It to Arcade Controls
You can do this even without a mame arcade cabinet, the only piece you actually have to have to make this really easy is a board made by a company called ultimarc, that emulates a keyboard. The board is labeled with each button name, and all you have to do is plug in the wire for each button and you're ready to play. Super super easy.
you can get the I-Pac board from ultimarc from HERE
I have an old version of the board, the new version looks smaller and cleaner. Very worth the money.
Step 4: PLAY
It's really fun to play and works really well. My good friend, and youtube star, Zack Scott and I are going to be putting up a video next week of us playing it. Look for it on Zack's Youtube channel at http://www.youtube.com/ZackScott