The invention is a device consisting of at least one body position and activity sensor, at least one peripheral temperature sensor and at least one light sensor, configured to provide information on the circadian system status and the sleep-wake status of an individual based on the data obtained from said sensors. It can be placed on the wrist of the subject, or on the subject's arm. The device may also include a blood pressure sensor. This device may be used in general studies of the human circadian system and, more specifically, for the study of sleep-wake and blood pressure rhythms.