For you iPhone 3GS users out there: go immediately to the App store and download the Yelp app. If you already have the Yelp app, delete it and go to the App store to re-download. Once you launch the app, shake your phone 3 times - no joke. It took me a couple tries (just throttle the shit out of it) and an Indiana Jones-like message will appear saying "the Monocle has been activated." Now you'll see an icon at the top called "Monocle" - tap it to start the augmented reality feature.

The 3GS is required - older 3G models wont work (you need the internal compass). If you don't have a 3GS, or an iPhone for that matter, go give Apple your money.