Imagine a world that's not completely and totally explored yet—sort of like in Warcraft where the unexplored terrain is dark because your character never went there. It exists in real life too. It's the own world you live in. You haven't seen everything or been everywhere so this app, Fog of World, makes the places you've already been completely clear and the unexplored places, foggy. As you go to new places, the map gets clearer. It looks so fun.
Not only does it motivate you to travel more (which is always a good thing) and see more and do more, it can also act as a great resource to keep track of the places you've been too. I haven't been this excited about an app since, I don't even know. If the battery drain isn't horrible, I'm definitely going to use this. $5 [iTunes via Fog of World]