Fcanas posted this news/release:

I put together a formatted string printer (printf) for the GBA. I wanted this functionality without a whole library to accompany it. It's not really intended to be used within a game, but it's a great tool for high-level debugging.

It requires one tiled background, a charBB, and a screenBB. All of those are configurable. It can print all ascii characters.

Check out the project's website:

http://code.google.com/p/gba-print/