A camera connects to the GBA slot, and the DS perches on a stand, pointing the lens at the player user. Face Training then seems to monitor and rate your ability to smile. Aside from physical therapy, we're not sure where the market is for this game application. Maybe Japan has more of a need to practice eyebrow movements than we ever realized.
See the trailers after the break. (Or for an even longer look, visit the game's Japanese site.)