The PokéWalker is a device used to level up your Pokémon while walking, you are correct. However, it does become a little more complex on what it may do. For instance, you are also eligible to capture Pokémon within the PokéWalker as well as recieve items and unlock events through different courses of the device. It should be very useful for those who wish to use it and also promotes physical activity for players.ok just a little confused here....... I've seen pics of it, but what does it do? i'm kinda getting the idea that it trains when you walk?
Seeing as a lot of people who will be playing the game attend school (which involves walking every so often or more) it will be very helpful to allow levels to be raised as well as gaining a few other benefits as mentioned.
For more information on the PokéWalker, you can read more here: Serebii, The PokéWalker also the HG/SS FAQ has a handful of information on the PokéWalker and how to use it.