In this work, we examine the different types of user interactions and 
deployment issues surrounding large public displays. We then select and 
develop a usage paradigm in which people use personal devices to interact with 
large public displays. Lastly, we present a physical interface for interacting 
with large public displays based on camera-enabled mobile phones. Our 
interface uses both Visual Codes and optical-flow processing to support 
serendipitous interaction with large public displays.