A method of monitoring a subject includes positioning an earbud within an ear of the subject, wherein the earbud housing encloses at least one optical emitter and at least one optical detector, and wherein light transmissive material is external to the housing and in optical communication with the at least one optical emitter and detector via at least one window in the housing. Light is delivered from the at least one optical emitter through the at least one window and into an ear region of the subject via the light transmissive material, and light external to the housing is collected and delivered through the at least one window to the at least one optical detector via the light transmissive material. Motion of the subject is measured via a motion sensor, and signals produced by the at least one optical detector are processed to selectively remove effects from subject motion.