Editorial message: special track on ubiquitous computing

Ubiquitous technologies, infrastructures, applications and services that operate across physical environments (e.g. neighbourhood, home, car etc) will soon be spanning all the different spheres of everyday life. Ubiquitous computing places humans in the center of environments saturated with computing and wireless communications capabilities, yet gracefully integrated, so that technology recedes in the background of everyday activities. The ubiquitous computing world is largely defined by applications, which present an altogether new set of requirements. In order to assess the impact of ubiquitous computing and discover caveats as early in the adoption process as possible, we need to study and analyze working prototypes applied in real-life settings and scenarios. The special track on ubiquitous computing applications, now in its third year, provides a forum for the discussion of all types of ubiquitous computing applications and related specialized infrastructures built for the deployment of targeted applications. Individual papers place applications within their use context and introduce novel and appropriate interaction paradigms while at the same time addressing related technical and business aspects and consequently identify novel opportunities or constraints