GRECO is a french ANR (National Research Agency) project whose aim is to design an energy efficient wireless platform that would be totally autonomous thanks to energy harvesting capabilities and adaptive power managing. To reach this goal, GRECO partners are developing a complete modeling that will be used to evaluate the different power optimization strategies leading to energy neutral operations. The power manager can tune various parameters at the different layers of the protocol stack, but this demo illlustrates the behavior of the power manager at the MAC layer only by adapting the wake-up period of the nodes.