Wireless Sensor Networks (WSNs) are a valuable technology to support countless applications in different areas. Given the WSN nodes resource constrained characteristics, designing energy-aware applications, communication protocols and security mechanisms are critical. The Operating System (OS) running on the WSN node also interferes with the node overall behavior and its energy consumption. In view of a variety of WSN applications, there is a need of developing a self-adaptable and self-configurable embedded Real-Time Operating System (RTOS).