Alright this was announced just under a hour ago on Japanese TV, and of course Pokemasters was able to get the information posted before anyone else
It's called Pokemon Walker or already dubbed PokeWalk, it's a Pedometer that contains various minigames, one being able to search one of five grass patches for Pokemon sprites to battle. It also allows you to take ONE pokemon out of your Heart Gold/Soul Silver games, and walk with it. Each step gives you more EXP and Happiness toward that one Pokemon before being placed back in the game.
Mods: I figured I would make a topic since this is some what big news, and just in case people do not check out the Announcement thread, feel free to merge it back if you want.