Inattentiveness is one of the major causes of traffic accidents. Advanced car safety systems try to mitigate this by detecting potential signs of distraction or tiredness, and providing alerts to the driver. In this paper we present CapSeat - a car seat equipped with integrated capacitive proximity sensors that are used to measure a wide range of physiological parameters about the driver. This can support safety systems by detecting inattentiveness and increase passive safety by facilitating suitable seat adjustments and posture detection. We present a sensor electrode layout suitable for detecting the necessary parameters and processing methods that acquire multiple physiological parameters from sensor data, using a variety of different algorithms. A prototype of the system is presented that was evaluated for all detectable parameters in a proof-of-concept study. We achieved a classification precision between 95% and 100%. Author Keywords Car seat; capacitive proximity sensing; dri...