London Streetmuseum app: Not really a social medium but a brilliant example for digital storytelling. With the StreetMuseum iPhone app from the Museum of London you can look at historical views of the city while you walk through London.
john littleboy is raising funds for Gizmo: Augmented Reality Greeting Cards. on Kickstarter! Gizmo greeting cards give you and your loved ones a stunning experience using augmented reality and your smart device.