Jeff is an ER doc (as well as the brains behind Alchemist) and he helped me out the other day with some gnarly metal that got in my eye - so in exchange, I built him this (prototype) bike mower.
It works pretty well, but the gearing (22x14 fixed) is way too high - I'm thinking you'd want more like 1:1 or even lower. Pretty fun idea, though, even if it's not too practical for steep hillsides or tight areas (though with the fixie, it's easy to back up). I think we can make it into the Daily Camera with this, so we gotta plaster some Alchemist and WW stickers all over the place.
I apologize for not wearing my helmet (in fact, I did almost crash at one point...)