Sorry, I should have made it clear that I didn't make that video, but its the same as the AR method for booting homebrew from the gamecube. I don't have my Wii yet so I couldn't confirm it, but as soon as I receive it, I'll do that for everyone.
You need a GameCube SD adaptor (SD Gekko, I got mine from Gameparts.biz), and an Action Replay Disc as well as the AR memory card. Basically you use your PC to make the SD card bootable a certain way, using the SDLoad software. Then, you put the AR memory card in GC slot 2, the SD card adaptor in GC slot 1, and boot the AR disc. A certain code is entered in, (its found in the SDLoad text info) and you start the game. The AR code is used to patch the AR disc, instead of patching any other GC games. That brings up the SDLoad screen, and you can load any GC .dol file. However, nothing that uses the disc drive will work properly on the Wii.