Modeling behavior has been a core topic of Psychology and the Social Sciences since their respective inception as academic disciplines. This has resulted in a fractured landscape of different theories, all addressing different aspects of behavior. At the same time the need to formalize the design of computer and smartphone applications has spawned the field of User Experience (UX). With the convergence of everyday behavior and the use of mobile devices the overlap between these two fields becomes ever more important. In this paper we present a comprehensive model of behavior, integrating five well-established theories, with the aim of creating a design framework for smartphone applications that foster motivation and promote the execution of a target behavior. The operationalization of the approach is demonstrated by showing how to design and implement a prototypical application to support healthy and sustainable grocery shopping behavior. While the framework proposed is not limited to this application, it is used to exemplify the relation with previous design approaches, and the concrete implications of the model-derived framework on its implementation. Our view is that both areas of research can benefit from each other: findings from behavioral theory can inform application design, while at the same time the ubiquitous integration of mobile applications allows to dynamically apply, operationalize, and implement behavioral models into everyday life.