Thanks so much lagman, that's definitely the post of the day!oh yah, there are two GBA emulators in development for the DS, they're both actually being made specifically with the R4 in mind
you can find the first one here
and the second one here, I hope I don't get in trouble for that second link, it actually supplies a few roms, so hush hush
I have geclicked but the web isn't gekommen.