After a long wait due to delays, and a release of the application in Japan last week, Pokémon Bank is now available to download for the 3DS in European territories, as well as Australia and New Zealand. There is no word yet of a North American release date.
The app (which is currently available for a free trial until March 14!) allows players to transfer their Pokémon from past generations into Pokémon X and Y, and presumably other Pokémon games that may come out in the pipeline. However, due to the framework of the games, only the Black and White titles (both 1 and 2, thankfully) can interface directly with Pokémon Bank, and to transfer Pokémon from yet more generations to Black or White, you must beat the game first.
I smell a Backlog/Continue review in the near future…
Even if this entire concept sounds absurd to you, go on and download it if only for the sake of nabbing yourself a free Celebi. You know you want to.