A motion detection system for detecting movement and/or breathing from a subject, e.g., for preventing SIDS, can incorporate a sensor in communication with a fluid-filled chamber while optionally combining audio and/or video monitoring systems. The sensor module may have a housing which can be attached, e.g., to an article of clothing worn by the subject. The sensor may be entirely enclosed within the housing which may also be filled with a vibrationally transmissive medium which transmits movements from the subject such that these signals impinge upon the sensor which captures these signals (or the absence of these signals) for processing and possibly alerting a parent or caretaker.
