An electrically-powered, wearable device (e.g., wristband, watch, finger probe, head-worn sensor) designed to continuously or intermittently measure and record multiple physiological parameters [e.g., heart rate, respiration rate, electrocardiograph, haemoglobin oxygen saturation (Sp02), routine body movement] using one or more technologies [e.g., photoplethysmography (PPG), reflectance pulse oximetry, electrocardiography, accelerometry). The data is typically transferred to a local application (e.g., smartphone) or central database for analysis, which might include evaluation of lifestyle factors (e.g., energy expenditure, activity level, sleep patterns).