I've messed with using a 9-button dance pad as an impromptu midi controller - gives you a full octave and you use the center square as a "rest", but I can't imagine trying to use it in a live setting - it would be like trying to play a guitar in a bouncy castle.
Is that possible, given that you only have two feet?
Are you looking for a mode which allows you to select a chord rather than just a single note? (One foot for the root, and the other selects single/major/minor/etc)?
I've been looking at accordion keyboards - with the accordion layout you get 100+ buttons and you only need to push one to get a chord. However at the width of a foot that is too big, and so I'm not sure if I take a simplified layout or just a smaller version of that.
