With regular usage of the Pokewalker included with SoulSilver, you can obtain Watts that can be used to unlock special courses that hold unobtainable pokemon in both HeartGold and SoulSilver versions. Watts are not total obtained, but collected in the game after returning from a stroll or sending gifts back to your game. There are also several routes unlocked by Nintendo Wifi Events and specific pokemon.

Unlockable	How to unlock
Amity Meadow	Unreleased to all versions.
Beautiful Beach	Collect 200 Watts.
Beyond the Sea	Trade for an International Pokemon in the GTS in Goldenrod City.
Big Forest	Collect 40,000 Watts + National Dex.
Blue Lake	Collect 2,000 Watts.
Dim Cave	Collect 1,000 Watts.
Hoenn Field	Collect 5,000 Watts + National Dex.
Icy Mountain Road	Collect 30,000 Watts + National Dex.
Night Skys Edge	Obtain the PokeDex Data for Jirachi.
Quiet Cave	Collect 100,000 Watts + National Dex.
Rally	Unreleased to U.S. versions.
Rugged Road	Collect 50 Watts.
Scary Cave	Collect 20,000 Watts + National Dex.
Sightseeing	Unreleased to U.S. versions.
Sinnoh Field	Collect 25,000 Watts + National Dex.
Stormy Beach	Collect 65,000 Watts + National Dex.
Suburban Area	Collect 500 Watts.
The Resort	Collect 80,000 Watts + National Dex.
Town Outskirts	Collect 3,000 Watts.
Treehouse	Collect 15,000 Watts + National Dex.
Volcano Path	Collect 10,000 Watts + National Dex.
Warm Beach	Collect 7,500 Watts + National Dex.
White Lake	Collect 50,000 Watts + National Dex.
Winner's Path	Nintendo Wifi Mystery Gift from 05/06/10 to 06/25/10
Yellow Forest	Nintendo Wifi Mystery Gift from 04/01/10 to 05/05/10