Mobile applications play an ever growing role in everybody’s life around our globe and the leading app stores currently offer more than 2 million different apps each for their users. It is well accepted that the usage context is much more important in the UI and UX design of these apps than when designing desktop applications. It is important to realize that a lot of these apps are part of a mobile service that defines their usage context and the UX of the mobile app is not only determined by the interaction with it but by the value creation of the whole service. We therefore propose in this paper a joint service and app design process that not only optimizes the user interaction with the mobile app but also the UX of the whole service in order to provide an optimal value proposition to the service customer of the mobile service