There's an FFIII rom for NES. There will probably soon be an FFIII DS rom too, but there's no working emulator yet, and an emulator would require an overly fast CPU anyway.

Does anyone know what the special characters can do to help your battle? I think Princess Sara and maybe Elia can heal your party, but what about Cid, Desh and Allus? It will be interesting to see what Dorga and Unne can do, although I have a feeling they won't be casting Meteo. That would be too overpowered.