Neat. Any thoughts on what the revenue model might look like? My first inclination is that this might not be a big enough problem, but there are a number of examples of recurring group activities where prior confirmation is useful - running groups are the first one that immediately came to mind.

I think the core of the idea is more "really simple RSVP" and much less about carpooling. With that focus, there are probably some really nice ways to simplify even further...