I have to admit I clicked just to hear on which side you'd stand on the walk 'em / whack 'em pronunciation divide. :-)
Nice job reverse engineering! Makes me think what else one could do, using just coils and simple logic for NFC communications.
There's a tradition in a part of my town of having an "advent calendar" of sorts that is made up of windows in people's houses. People have various kinds of displays, and every day until Christmas another one is revealed.
One of the participating houses had some sort of capacitive touch sensor made from aluminium foil on the inside of the glass last year, and you could use that to turn lighting on, and trigger some event in their display IIRC. Now I'm thinking a coil and a few simple logic ICs is something you could give away to let people interact with art, or whatever weird project one might have.
Watching the (previous) USB and tablet video now, great stuff. At the risk of seeming like a weirdo, I found the low-level legacy and dirty protocol hacks part really interesting.