Pokéwalkers are small pedometers, they originally look like a normal Pokéball (red top and white bottom) and were a free bonus bundled with Pokémon HeartGold and SoulSilver Versions for Nintendo DS. If you connect it to the game using infrared signals, you can transfer a Pokémon from your box to it and take it for a walk on a road you can choose. You will earn one watt every 20th step you take, they can be used for mini-games you can find items or catch Pokémon with. Several watt will unlock new roads where new items and Pokémon can be found. You can also collect items and watt if you connect your Pokéwalker to another one.
My Pokéwalker icons are free to use avatars for deviantART, you can customize them with any Pokémon sprite you'd like to have inside. The sprites of all Pokémon from generation one to generation four can be found here [link] (animated) and here [link] (not animated).
The whole Pokéwalker Collection can be found here [link] If you want so see an example of an finished avatar, please click here [link]
Feel free to use them for whatever you want - but make sure to link back to my profile or the original artwork! ..and it would be nice if you'd show me your finished avatar, too