A monitoring device configured to be attached to a body of a subject includes a sensor having at least one optical emitter and at least one optical detector, and a processor coupled to the sensor. The processor is configured to instruct the at least one optical emitter to emit a different wavelength of light into the body of the subject during each of a series of respective time intervals. The processor is configured to measure a respective different physiological parameter from signals produced by the at least one optical detector upon receiving light from the body of the subject during each of the respective time intervals.