Nintendo has recently trademarked the 'DS Houi Sensor Card', 'Houi' being the Japanese word for 'Direction'. A likely guess for what this means could be motion-sensing DS cards, similar to the Gameboy Advance games 'Yoshi's Universal Gravitation' and 'WarioWare: Twisted!'. However, what the 'DS Houi Sensor Card' really is is anyone's guess at this point, and they may not even be released outside of Japan. Or at all..
Source: GoNintendo