The Walt Disney World park is utilizing a DS game called the Disney Magic Connection to give you real time info on the park (note, this is in beta and probably not available everywhere just yet). Details are vague for now as there hasn’t been an official press release.
From what I have seen, this is a really awesome thing for Disney. Disney Magic Connection shows you the Park Map, where the nearest bathrooms and ATMs are, ride line times, when and where character showings and parades are occurring. It even has a few games and a wishlist (great for making a list of stuff to do while you are at the park). Another cool feature, the app detects when you are on a ride or in the queuing line and goes to sleep automatically.
Unfortunately, the current app is only for Disney handout DSes (I assume it needs a card and can’t be downloaded like a demo) and not your own DS.
You can checkout the guide manual here.