I just got the Olympus LC-63A screw-on, auto-opening lens cap for the XZ-1. It's a winner. I don't have any experience of third party caps that do the same thing, but I was warned off one. In any event, for $20 (on ebay) I think this cap is worth it.
I grew up having to take off a lens cap and pocket it, and never liked tethered caps flapping around under the lens. But having an auto opening cap on a point and shoot just makes the whole experience -- well -- more point and shooty.
Anyway, the Olympus cap in this instance is worth the price, unlike some of their ridiculous $60 plastic hoods. IMHO.
OOPS! I JUST NOTICED I PUT THIS IN THE WRONG THREAD.