It's called Bionic Eye, and it's not entirely sure it's legal (Apple said they'll let developers create AR apps come September; well, September is here, but we're not sure the embargo has been lifted), but it's currently available in the App Store. It's a pretty straightforward take on AR, letting you visualize Points of Interests located nearby in all US cities. It also works in the UK, France and Tokyo.
Now, before we continue, we must mention that several apps dabbled with AR on the iPhone before; Yelp hid the functionality as an easter egg, while an app called Metro Paris Subway did something similar to what Bionic Eye does, but only in Paris.
Bionic Eye will likely receive far more attention due to the fact that it works accross the US, letting you visualize locations such as restaurants, coffee shops, Apple stores, and various tourist locations. In vertical position it gives you a 360-degree view of all POI near your location, updated in real time; when you flip it to horizontal position, you'll see a list of all the nearest POI. Check out a video demonstration below.