The night guard concept you mentioned is essentially the idea of Baldy's basics. (Just the first example I thought of, I don't know if there's a better example out there) You need to move around a building to accomplish a goal, while an AI patrols the halls and you need to avoid it in order to complete the game. I'm still spinning my wheels a bit, mostly because this theme isn't really sparking my interest, but I'm hoping to come out at the end of this week with SOMETHING.