Stress is an important aspect of mental health which impacts on wellbeing. Wearable devices are increasingly used to help people deal with stress in daily life. However, most of the current applications focus on detecting and representing physiological data. In this paper we report on the design of an integrated wearable system composed of physiological sensors and a self-reporting interface. Through an iterative design process, we developed two prototypes and evaluated their technical performance in a laboratory condition. We elaborate on the issues we have encountered and addressed in the design iterations. We discuss how these lessons might contribute to the design of integrated sensing systems in real life. We end this paper by reviewing limitations of the study and directions for future work.Keywords: smart wearables, stress management, design for mental health@en