From Acrossair :
Fans of Twitter behold - the 1st Augmented Reality Twitter app has just landed to feed your thirst for news and views everywhere.
Holding the phone up vertically shows all the tweets around you in 360 degrees of Augmented Reality view, with the distances and photos of the people tweeting around you. People you are following are highlighted in blue and sliding your finger up and down allows you to see tweets that are further away. You can access your profile at any time using the 1st icon on the bottom left of your screen. On the main AR view via the bottom menu bar, you can refresh all the tweets around you by clicking the refresh button, add more tweets by pressing the '+' button. Clicking on a tweet in either 2D or Augmented Reality view will allow you to see all the tweets by that person.
You can download Acrossair on iTunes here or on your iPhone there (1,59 €) :