ChattAR is a Facebook client by QuickBlox with extra features of Public Chat room (!), Location based chat (!!) and Augmented Reality Chat (!!!). Moreover, the source codes are open so go ahead and build your own app with these features.
Find the source code and more information about ChattAR in our Developers section: http://quickblox.com/developers/Chattar
Download app from AppStore: http://itunes.apple.com/us/app/chattar-for-facebook/id543208565?mt=8