Accurate power and performance figures are critical to assess the effective design of possible sensor node architectures in Body Area Networks (BANs) since they operate on limited energy storage. Therefore, accurate power models and simulation tools that can model real-life working conditions need to be developed and validated with real platforms. In this paper we propose a sensor node platform designed for health-care applications and a validated simulation model based on event-driven operating system simula- tion that can be used to accurately analyze performance and power consumption in BANs composed of multiple nodes. Thus, this model can be employed to tune the node architecture and communication layer for different working conditions, applications and topologies of BANs. In this paper we validate the proposed simulation model on different real life applications and working conditions. Our results show variations of less than 4% between the presented simulation framework and measurements in the final platforms.