Abstract: Device, system and method to monitor user breathing patterns utilizing posture and diaphragm (breathing) sensor signals. The user worn device comprises a housing attached to a retractable belt that is worn around the user's trunk. The housing contains both posture and breathing sensors. The device monitors the output signals of these sensors and measures the state of both the user's posture and diaphragm (e.g. changes in the belt's length or force on the belt as a function of user breathing) to analyze breathing signals. The system's processor receives, processes, and transmits sensor signal data, and can also calibrate and interpret these signals utilizing various algorithms. In a preferred embodiment, the posture sensor is an accelerometer, and the retractable belt winds around a spring tensioned spool in the device's housing. The software can produce posture adjusted user respiration data, and can also be used for breath training and other purposes.