I've never really written anything that isn't purely numerical (and therefore purely terminal-based) and purely C++. So it'll be a big learning experience.

The calculator that comes on the pre is absolute shit, and every once in a while I could use a better one. So I'm thinking about writing an RPN calculator. Assuming there are some reasonably acceptable math libraries to work with, it should be quite straightforward, just a few steps up from a Hello World.