The Pokéwalker was a pedometer originally bundled with copies of with Pokémon HeartGold and SoulSilver. A Pokémon from one of those two games can be sent to the Pokéwalker, where it will gain experience points from the steps the player takes in the real world. A currency called watts also builds up as steps are taken, and can be used to purchase one-time use items that offer a chance to find an item or catch a wild Pokémon. Three items and three captured Pokémon can be stored on the device, and will be sent back to the Nintendo DS game the next time the Pokéwalker communicates with it. The Pokémon and items that can be found depend on the location selected when a Pokémon is sent from the Nintendo DS. Two courses are available at the start, and more can be unlocked by accumulating a certain number of watts, performing a specific task in HeartGold or SoulSilver, or receiving a special Wonder Card from an official event.