The emergence of powerful digital infrastructures, wireless networks and mobile devices has already started to move computing away from the desktop and embed it in the public spaces, architectures, furniture and personal fabric of everyday life. Handheld and wearable computers, mobile phones, digital cameras, satellite navigation, and a host of similar devices join the Personal Computer as commonplace digital tools. We are increasingly becoming accustomed to using a heterogeneous collection of computing devices to support a growing range of activities. These embryonic forms of ubiquitous computing technology have already had a major impact on the ways that people work, learn, entertain themselves, and interact.