Install and run
DarwiinRemote on your Mac -- you must have Bluetooth. You will need to map the keys for the remote with the above app to some keyboard keys. The default setup is for Front Row. Create a new set not using any Front Row keys. Now with your game emulator, map it to the same keys on your keyboard. Now you can control your game emulator using your Wii remote.
Due to a big bug in Open GL, if you have a big LCD like me, your Mac (Mac mini here) will crash when you try play in full screen mode. There is a workaround. For
Snes9x, you can choose any non OpenGL display in the prefs. For
sixtyforce, up the screen resolution to its highest setting. I haven't tried any other emulators yet.