Running this channel will completely turn off the Wii system (red light) so you don't have to. That's it.
If you use a USB hard drive, the Wii still sends power to the USB ports and your USB drive remains powered on.
Reset and Eject
There is also another version which also ejects the disk and gives you the option to reset the Wii by pressing A.
The download file contains two homebrew WAD files, one for the original and another for the reset and eject version. Installing either one will create a channel that will power off the Wii system when started. (They both take up 8 blocks.)