This thing's called the Wii Recovery Dongle. You clip it into your Wii's GameCube memory card slot and, if you're in possession of a bricked Wii, it might (provided you've got the skills) just help you save your console. Might. To be honest the specifics are waaaaay over our heads, so if you've got a dead Wii on your hands and would like a more detailed run-down, the kids at HackMii are the ones to see.
Wii Recovery Dongle [HackMii]