Body sensor networks (BSNs) have originally emerged as a potentially disruptive technology for continuous physiological and behavioral monitoring of users. After more than a decade of their introduction, researchers have addressed a number of important research challenges. The research community, however, further needs to deal with more innovative concepts focusing on autonomic, cognitive, and smart BSNs at each level of the BSN architecture: sensors, device, networking, middleware, multi-sensor data processing and fusion, systems, and data and semantics. In addition, the proposed Special Issue targets the latest research findings on the analysis, definition, implementation, and innovative solutions related to models, architectures, algorithms, protocols, signal processing, hardware at sensor, system, and systems-of-systems level toward the design and development of cognitive BSN ecosystems. Next generation of BSN architectures (namely, BSN 2.0) will be also synergistically merged with the Internet of Things technology to foster several application domains: healthcare, fitness and wellness, smart cities, smart factories, on-field emergency management systems, and so on.