Ambient and mobile systems consist of networked devices and software components surrounding human users and providing services. From the services present in the environment, other services can be composed opportunistically and automatically by an intelligent system and proposed to the user. This article first presents an illustrative use case, then explores the requirements and formulates related research questions. Next, it describes our approach aimed at answering the requirements, based on distributed artificial intelligence and multi-agent systems. It reports on the development of a prototype solution, and analyzes the current status of our work towards the different research questions that we have identified.