AA batteries are a really stupid choice imo, but its a nice idea. the annoying thing is, it'll take extensive modifications to make that stuff run off of lithium, unless they happen to pick a voltage that is a multiple of 3.7 which is unlikely because AA batteries are 1.5v. at least there's cadmium and nickel hydride as rechargeable alternatives to single-use alkaline batteries.
i wish them success in any case. the more open hardware out there the better :)