The 'patent or not to patent' issue caused me some anguish. In the end, I decided that the potential market is probably fairly small, and probably not worth the effort. I might submit it for Alpkit's CoLab09 competition, though, just for a bit of fun. I have other ideas that I'm still musing on patenting, as the market is much larger, I know how to make them, and there'd be a healthy profit margin. Naturally, I'm staying schtumm...
It's possible that someone in the US snaps the idea up, but good luck to them if they can find a way to make them; I thought of all sorts of Heath Robinson contraptions to do it, but the dual fold is a rather nasty thing. I'm sure someone with a packaging background (e.g. folded card) could do it.