Interesting stuff, Matt -- looks like it's based on (inspired by?) the stepping machines in the gym. Best thing is that you actually go somewhere when you're using it.
I don't have the photo handy right now, but a year or two ago, my niece's daughter was using a pontoon bike on a quiet pond in Germany -- kind of a vertical version of a pedal boat, a paddle wheel on the stern, a rudder activated by the handlebars, with a couple of outrigger pontoons for balance. Looked like a gimmick as much as anything, but I could imagine a game of water polo played with those could be a bit of a hoot.
Cheers, John