Methods and apparatus for monitoring a subject are described. A monitoring device configured to be attached to a body of a subject includes a sensor that is configured to detect and/or measure physiological information from the subject and a motion sensor configured to detect and/or measure subject motion information. The physiological sensor and motion sensor are in communication with a processor that is configured to receive and analyze signals produced by the physiological sensor and motion sensor. The processor is configured to process motion sensor signals to identify an activity characteristic of the subject. Once an activity characteristic is determined, the processor is configured to select a biometric signal extraction algorithm or circuit in response to the activity characteristic of the subject, and then process physiological sensor signals via the biometric signal extraction algorithm or circuit to produce physiological information about the subject.
