The present invention discloses a mm-wave radar sensor to be deployed in the vehicles for seat occupation detection applications. The key system relevant components are utilization of mm-wave integrated radar, specific planar high-gain antenna radiation pattern, and analyzing of the heartbeat and optionally also respiratory dynamics. The method of operation calculates probability of the seat occupation event regarding: detection of the passenger on the seat, detection of a baby or a child on the seat, detection of the presence of a baby or a child in the vehicle after the driver has left the vehicle, detection of the human or animal presence of intrusion in specific vehicle environment. In case that probability is above a predefined threshold, typically the interaction with vehicle control system is initiated using arbitrary automotive interfaces. Corresponding predefined actions are taken in that case. The predefined actions could be one or combination of the following: audio signal alerts to driver, inside cabin light condition change, engine operation condition change, opening of the windows or corresponding communication using arbitrary wireless means to outside vehicle environment. Optionally, the system is utilizing additional parameters like vehicle cabin temperature and/or timing information about engine stop and driver leaving the car. Preferably, the system is using 60 GHz or 77-79 GHz integrated radar front end working in Doppler operation mode, with 4×4 Tx and Rx planar radiation elements, with physical size typically in the range 4×2×1 cm, or smaller.