Yeah, it's a 3DS download game. 3$. It's basically another Augmented Reality game, but you catch DW Pokemon in it, and can transfer them to BW2. The Lvl they import at is determined by the number of badges you have. After collecting the Tornadus, Thundurus, and Landorus, you can insert 4th gen games to unlock the respective game mascot. Hence, lots of Lvl 5 legendary Pokemon! If I have the patience that is. I already have Tornadus' Therian Forme (that's how you get them btw). They also all have DW abilities.
Several non-Legendary Pokemon are also catchable in the game. It's really fun, I recommend it.