This paper presents a novel device that uses low-cost sensors to provide continuous monitoring of driver motion and detection of driver behavior. The data is processed in real time. The device consists of wearable head, neck, and torso units, each equipped with an Inertial Measurement Unit (IMU) that measures linear acceleration and angular rate data of the driver’s head, neck, and torso while the vehicle is in motion. A series of experiments were designed to validate the device by testing it in a real driving scenario. During these experiments, the subject was required to perform a continuous driving task that included a variety of maneuvers, such as straight-line driving, braking, roundabout driving, lane changing, and yielding on an urban road with no traffic. The tests were carried out to simulate both normal and aggressive driving. The results of the experiments are discussed in order to confirm that the device is capable of monitoring driver behavior and can be effectively used to monitor activity and alert the driver.