Nintendo has just confirmed that when you create an account on the WiiU, it is permanently linked to that console. Currently, there is no way to transfer your account to a new console, should something happen to your WiiU. Your account data includes saved games and console settings.
You, also, can not log in with your account details on another machine. If you were hoping you could log onto your account while at your friends house, you may be disappointed.
There are plans to change this according to the Nintendo support page, but as it stands now your info is locked to the console. Be careful and take care of your WiiU and hopefully this situation will get rectified soon.