(via YouTube)This video is just a controlled example of what could be possible when Minecraft comes to the smartphone market. Using Kudan's Qoncept augmented reality engine which requires no QR codes to work, it is possible to use symbols such as manholes and drains as markers for the engine, which can then render an augmented Minecraft scene.
This idea could even be developed substantially with the use of the smartphone GPS into a real, location-based Minecraft adventure...
http://www.kudan.eu