DeSmuME Wii r154 released by Arikado, scanff and several other developers.
DeSmuME Wii is a port of the Nintendo DS emulator DeSmuME to Wii homebrew.
Installation
Download the latest featured release off of the google code SVN downloads tab.
Extract the .zip to the root of your SD Card or USB Device
Place ROMs in device:/DS/ROMS/
Saves are put into device:/DS/SAVES/
If you'd like to use a BIOS place it in device:/DS/BIOS/ named biosnds9.rom and biosnds7.rom