Who Owes Who launched in the App Store today; it simplifies the task of splitting up group expenses. You enter payments along the way, be it a road trip or planning a big event, and designate who paid and who should share the cost and the app will show you the payments required to even up. Costs can be split evenly or by % or weights. Someone not drinking? Easily exclude them from the tab for the beer run. Multiple currencies are easy to enter if traveling internationally. Only US$ 1.99 on the App Store.