I just got word that the latest version of Yelp iPhone app brings a very interesting new feature: augmented reality. Simply put, you point your camera to a location and Yelp will try to match that against their existing reviews database.
Activating this feature seems to be quite geeky or magic though:
So you shake your iPhone 3 times. That activates a feature called Monocle. A message should come up if you activated it. A blue box will come up saying “the Monocle has been activated.” It will create a button in the top right corner. Now you should be able to look at the bars, restaurants, etc. Only works on iPhone 3GS
— via Scoble
Make sure you are checking the other apps in the iPhone apps for geeks series and the iPhone apps promotions.
In case you want me to review/test an iPhone app feel free to drop me a code. You can contact me at iphoneapps [at] mypopescu.com