I know people who, if they were for example taking a long cross-country trip, would split up gas, hotels, meals, etc., down to the penny. I even heard of somebody who hounded one of his friends for $1.72 after the trip was over. This app sounds perfect for them. Still, I can't believe there's much of a market for them, since anybody who's cheap enough to care about $1.72 from a friend would never pay for this sort of app in the first place.