Pre-order Kingdom Hearts 3D: Dream Drop Distance ahead of its summer release and you'll get some augmented reality cards to use in-game.
The AR cards unlock exclusive Dream Eaters, though retailers haven't specified whether the cards unlock evil Nightmare Dream Eaters to battle or helpful Spirit Dream Eaters to recruit and level-up. We'd wager on a combination of both.
So far you can pre-order with Amazon but seeing as the listing says the cards come in the game box, we reckon this offer will be rolled out to other retailers in due time.