YKB posted this article only a few days ago. It seems the device has been officially announced.
This appears to be some sort of new device that senses which way you move the DS just like an optical mouse. It also seems to act as a "rumble pack" as seen in the demonstration video. Since I can't read Japanese I am unable to share anymore information. I wonder how Nintendo will implement this new device... and how our homebrew community will use it too.