Determining the orientation of proximate mobile devices using their back facing camera

Proximate mobile devices that are aware of their orientation relative to one another can support novel and natural forms of interaction. In this paper, we present a method to determine the relative orientation of proximate mobile devices using only the backside camera. We implemented this method as a service called Orienteer, which provides mobile device with the orientation of other proximate mobile devices. We demonstrate that orientation information can be used to enable novel and natural interactions by developing two applications that allow the user to push content in the direction of another device to share it and point the device toward another to filter content based on the device's owner. An informal evaluation revealed that interactions built upon orientation information can be natural and compelling to users, but developers and designers need to carefully consider how orientation should be applied effectively.