This thesis project is about an innovative solution to reduce road accidents, specially focusing on those caused by drowsiness, which are estimated to be 15% to 20% of the total number of crashes and often resulting in the most severe injuries. The project consists in a wearable device that monitors the physiological state of the driver; this, respect to the camera-based DMS, is faster and more reliable because detects the state of the driver before he is completely asleep (eyes closed), when may be too late to prevent an impact. The system architecture can be subdivide into three intercommunicating layers: • Sensing layer The state of the driver is measured with a Polar OH1+ sensor, that is an optical sensor able to monitor heart rate with PPG.