wow missed that found it on youtube good the things people will come up with for attention on youtube.
I think the OP is talking about that totally fake video on youtube that projected a keyboard on a table and you could type on the table basically.
If thats not what you are talking about, here are some cool augmented reality apps
http://www.tripwiremagazine.com/2011/07/45-brilliant-augmented-reality-iphone-apps.html