Given that Emulators are in a bit of a gray area in the law I'm not sure it's actually safe to discuss them here.
In any case I've done a search online and turned up one possibility (checking it shortly), but you -may- have also misunderstood what it seems an OVERWEALMING number of these are. They aren't emulators for the Wii as in Wii on PC, they're emulators for other systems on the Wii (NeoGeo on the Wii, Genesis on the Wii, etc.)
EDIT: I did locate one however I will clarify right now if it actually works, I would have to say it violates Nintendo EULA. I'm not positive on its legality but it doesn't appear to need Bios or anything to run it - that generally means it's violating SOMEONES rules somewhere XD
Edit 2: Yeah somethings an EULA violator here. It literally has everything it needs to play GC games, let alone Wii games, so my very law-abiding guess is this may very well get shut down sooner or later for TOS/EULA violation by nintendo. Assuming it works with Wii, which it probably does.