quite old info but for people who haven't had a chance to look around:

so finally, the augmented reality app became real!!! we've made numerous concept movies from the college time using this AR idea, and iPhone OS 3.1 makes dreams come true :) it's still debatable (because of window 7) but still i believe apple rocks, window is lame! go apple!!

http://mashable.com/2009/08/27/yelp-augmented-reality/