Had you ever been standing on top of a mountain or a high building and you saw something like a building or an interesting object at the horizon?
The FindHorizon app helps you to find out what you currently see at the horizon. Therefore the app uses the built-in compass of your iPhone (3GS and 4 only). After you hold the iPhone into the aimed direction you have to guess the distance to the object and then the app shows you the object on the horizon on a map.
It is very simple to use, but also very powerful and you can use it also in several other situations. Try it and you will love it.