If you’re looking for a review for Yelp, you’ve come to the wrong place. Reviews on it are really, really ubiquitous, so I won’t waste your time on another one. This however, is something different.

By this point, most iPhone users are already aware of this application. Maybe you use Yelp and love it for finding restaurants and bars, maybe you checked it out, but ditched it for Urbanspoon or another restaurant guide. Well, if you’re in the latter group, you may want to give it a second look.

Thanks to a tip from PD reader troublekid, who pointed me at a post on iPhoneFreakz.com, I discovered something really cool buried in this app.

If you’re not familiar with augmented reality browsers, they’re basically browsers or other apps that use a phone’s camera as a viewfinder, as well as GPS and compass, to display additional info about whatever’s in frame. So point your phone at the NY Public Library, and you might see info pop onto your screen about library hours, phone number and transit info on all the lines that go there.

Well, it turns out there’s an easter egg, or hidden feature, that lets 3G S  users trigger augmented reality functions in Yelp. Open the application, and then shake the iPhone 3 times to access a feature called Monocle. Activate it, hit the button on the top right corner and then enjoy some AR goodness.

Augmented reality was expected to hit the 3G S with iPhone OS 3.1 or later, but this gives us a taste of it ahead of time. For more, check out the video of it in action.

[via iPhoneFreakz, Mashable]