There are unofficial Pokémon apps, such as this. Nintendo and Game Freak are finally releasing an official Pokémon app for the AppStore and the Android Market.
The app, Pokémon Say Tap? BW, uses music and on screen Pokémon cards in a timing game. The free app is slated to be out this Australian winter, making it the first Pokémon game to appear on non-Nintendo hardware.
Well, besides those puck-based Pokémon arcades. Still, this is a big deal. Nintendo's making its first move onto smartphones.
ポケモンがついに公式でスマフォ進出！ 『ポケモン言えTAP？』今夏配信 [Kotaku Japan]