Infectus is a modchip for the Wii that can dump or restore the NAND, and connects to a PC via USB to send the dumps out.

Infectus
General
TypeHardware tool
Version2
Links
No Longer Produced
Peripherals
USB mass storage device

This is much harder to use than BootMii and Priiloader; it should only be used for bricks beyond what can be fixed with software.