Pokéwalker

The PokéWalker is a device that comes included with every copy of Pokémon HeartGold and Pokémon SoulSilver for the Nintendo DS. It is a pedometer designed to look like a Poké Ball. In the game, you can merge a Pokémon over to the pedometer wirelessly. Afterwards, each step you take will give one experience point to your Pokémon. Once you return, you can trasmit the data back to the game.