With mobile devices being an integral part of the daily life of millions of users having little or no ICT knowledge, mobile services are being developed to save them from difficult or tedious tasks without compromising their needs. Starting with a number of real life scenarios we have been working towards supporting end-users in managing their services in an efficient and user-friendly manner. We observe that these scenarios consist of sub-tasks that can be solved with collaborative service units. Therefore, a composition of such service units will serve the needs of the end-user for the complete scenario. We envisage that a visual formalism and tools can be developed to support these end-users in creating such service compositions. Moreover, methodologies and middleware can significantly reduce the complexity of developing composite services. This paper focuses on the role of ontologies within that context. Ontologies can assist the users in selecting appropriate services and setting composition parameters within a composition tool. For our prototype demonstration system we target the open source Android cellphone architecture supporting a number of different runtime platforms.