Users are making use of more and more devices like mobile phones, PDAs, laptops, stationary PCs, etc., and it is crucial to provide service continuity not only across heterogeneous networks but also across heterogeneous devices. Users should be able to use services with minimum interruption even when changing devices. This paper provides an analysis of the composition and distribution of generic mobile services. It then addresses the impacts these models have on service continuity across networks, devices and domains.