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 ...
One more GBA game to the list.
Ones with expansions are $30.
Prices of accessories to go up however.