The Swapnote app on the 3DS not only allows friends to send each other messages, but is also a breeding ground for creative ideas. One of the most innovative uses of the software so far is from a game design student called Ben Gray, who has devised an old-school Dungeons and Dragons-style RPG.
It may sound complicated, but the video below does a neat job of explaining how it can work. You can also check out the template below to get you started, while the home page for the video also has a lot of additional details.
'Swapnote RPG': it could catch on.