I’m still trying to figure out exactly what this thing does. According to Akihabara News, the Buffalo WCA-G features something called the AOSS system, which lets you play video games online without ever having to hop on your computer. Thankfully, it’s supposed to be a completely wireless system, so you don’t have to mess with ugly cables either.
The Buffalo WCA-G “takes care of the very first configuration itself and all you have to do is sit back and enjoy.” Based on this, I think that it acts as an intermediary between your video game console — Nintendo DS, Wii, PlayStation 3, whatever — and your router.
The controls look simple enough, but I’d imagine you’d still have to go through the configuration on your video game system before you can enjoy some crazy Tetris DS action online with Japanese players you can’t possibly defeat.