This morning, quite by accident, I learned that one of my co-workers (*) has written a mobile app/game (**) for backgammon -- eXtreme Gammon
Ah! Here is the mobile version
(*) he's a furriner -- a Frog, in fact! -- but let's not hold that against him. Or, not too much, anyway. ;)
(**) after looking over the linked site, I think I misunderstood him about it being a smart phone app. Perhaps what he'd meant is that it has been recently ported to those platforms.