June 7, 2009
It was announced on Pokémon Sunday that a new device, dubbed the PokéWalker, will be distributed in Japan to those purchasing HeartGold/SoulSilver this fall. The PokéWalker is essentially a pedometer, in the shape of a PokéBall, that will increase your Pokémon's experience and happiness as you walk. The PokéWalker allows for the transfer of a Pokémon from HeartGold/SoulSilver (compatability with other fourth generation games is unlikely).
Given the device's similarity to the Pokémon Pikachu 2, which was distributed in Japan during the releases of the second generation games, it is possible that the PokéWalker will not see distribution in other countries. If and when that can be confirmed we'll be sure to let you know!
The following YouTube video, showing the PokéWalker being revealed on Pokémon Sunday, was recorded by Filb.de.