Following the video posted yesterday on Pas Si Grave... here's another interesting app using the compass and the camera abilities of your new iPhone 3GS.
TwittAround allows you to actually see (thru your iPhone screen and Augmented Reality) where your friends are tweeting from, and how far they are from you.
Just watch for yourself!
How fun is the future...
Here, you'll find different uses for Augmented Reality and the iPhone.