Disclosed herein are methods and devices for monitoring a subject at rest. One such device comprises a sensing unit having a fluid-filled bladder configured to be placed under a substrate on which the subject lays and a sensor in fluid communication with the bladder. The sensor is configured to sense pressure variations within the bladder generated by a heart beat, respiration and body weight of the subject and to generate signals indicative of the pressure variations. A processor is configured to receive the signals and to determine and generate output indicative of the subject's heart beat and respiration and presence on the substrate. An external device is configured to display one or more of the output.