The use of wearable devices in daily activities is continuously and rapidly growing. Wearable technology provides seamless sensing, monitoring, multimodal interaction, without continuous manual intervention and effort for users. These devices support the realization of novel applications in many domains, from healthcare to security and entertainment, improving the quality of life of users. The situation awareness paradigm allows wearable computing systems to be aware of what is happening to users and in the surrounding environment, supporting automatic smart adaptive behaviors based on the identified situation. Although situation-aware wearable devices have recently attracted a lot of attention, there is still a lack of methodological approaches and references models for defining such systems. In this paper, we propose a reference architecture for situation-aware wearable computing systems grounded on Endsley’s SA model. A specialization of the architecture in the context of multi-user wearable computing systems is also proposed to support team situation awareness. An illustrative example shows a practical instantiation of the architecture in the context of contact tracing using smart sensorized face masks.