Today, Nintendo announced that the PokéWalker accessory, a Pokéball-shaped pedometer that interfaces with Pokémon HeartGold and SoulSilver, will be packaged with copies of the games when they arrive in stores on March 14. Nintendo had previously dated Pokemon HeartGold and SoulSilver along with the rest of its Q1 lineup, but it omitted mention of the accessory -- though the game's Amazon listing didn't.
The Pokéwalker allows players to earn "Watts" with their steps, which can be used both to catch Pokémon inside the device and unlock routes in the main game. In addition, the device enables wireless item trading between two Pokéwalker carriers. Gotta walk the mall to catch 'em all!