Here’s an interesting discovery: Nintendo has apparently region-locked the Wii U GamePad controller. Which means if you purchase a GamePad controller in Japan (which are sold separately at around $180), and try to connect it to your Wii U in the United States, it won’t work.
Wii U consoles are region locked, and so are the games. It seems Nintendo went the extra step and region locked a controller. As far as we know, this would be the first time in history that a videogame controller is region locked.
Nintendo currently only sells the GamePad separately in Japan, but will start selling them individually in North America and Europe next year. There are currently no games that support two GamePads, nor are there any games that have been announced to support two GamePads.