PocketNES is a NES emulator for the GBA. Author release notes:

Hmmm the verdict of the gbax.com competition seem to take a long time, anyway I fixed a little thing with the IRQs on PocketNES which affected Guardian Legend. I’ve also fixed the DAA instruction on the Z80 cpu core so it should be quite complete now (clears all the test on ZEXALL SMS version).

http://hem.passagen.se/flubba/gba.html