Ideally you should cleanly handle the power button and activation of the task switcher (Ctrl+Backspace). How to do this from SDL, I'm not sure. I assume some of the other games like SuperTux are SDL based and do these things properly. You could

• play with the games, see of they work, and go download the source (for example SuperTux source)
• Posting on maemo-devel mailing list which is a more targeted

As for hildon/SDL, I know for a while there was a game wrapper that had a hildon launcher for SDL(?) games. I think some of the builtin games use i(?). You could do similarly for a mixed SDL/Hildon experience.

I know, don't I sound so definitive