This paper outlines our current research program in the fields of ambient intelligence and context-aware computing and the tools we are building to accomplish this research program. From a discussion of our conception of mental models in the domain of ambient context-aware computer systems we derive hypotheses which we intend to test empirically. A modular framework for implementing and assessing situation awareness in humans and computers is introduced. We describe the framework's architecture and illustrate its suitability for its intended purpose. Finally, we present an outline of our next steps towards real world application systems for our research.