IMPORTANT:
There doesn't seem to be any voltage regulation, which means the output voltage is the same as the voltage on the input(usually the voltage of the car battery)
As voltage can fluctuate, particularly from a car cigarette lighter(due to car circuitry), this means too much voltage could potentially be supplied to the Wii.
-->> Because of this, it's possible the Wii could be damaged in certain circumstances, & I can't take any responsibility for any potential damage. <<--

However, this might be well suited for these uses:
- powering the Wii from a battery by itself, as the voltage shouldn't vary much from 12V.
- using the Wii power connector to repair a damaged power adaptor you already own.
- if you have electrical knowledge, you could add your own voltage regulator

Has a replaceable fuse inside(unscrew the tip to access it), which should help prevent too much current being passed through it. It won't protect it from over-voltage though.

ANOTHER IMPORTANT NOTE:
Do not plug THIS into the cigarette lighter socket of any vehicle that uses 24V - eg: some trucks, buses, campervans.