You can do lots of things with Gecko adapters!
I personally use USB Gecko which is better and really easy to transfer backups and gamecube saves to pc. Got it from
Adictron
They offer nice price with worldwide shipping and have in stock both SD Gecko and USB Gecko.
What can you do with SD Gecko? I think the proper question would be what can't you do with it?
You can:
-Play emulators with roms and saves stored in the SD card:
Tehskeen
Which emulators? Atari, NES, SNES, Master System, Game Gear, Genesis, GameBoy- GB Color- GBA, Scumm, PCE, Neo Geo Pocket, Neo Geo CD, MAME, Nintendo 64, etc
-Play GameCube backups stored in SD cards:
SD-Boot
-Play homebrew games and other scene applications as bioses
-Manage saves to pc (though this fails sometimes):
mcbackup
-Rip backups:
sd-dvd
etc
You can use Gecko products with a moded GameCube or a moded Wii.
You can also use them with an unmoded GC/Wii through SD Gecko + Action Replay method:
AR + SD Gecko
And seems that is in the work a way to play them on Wii only with the aid of an original Zelda disc.