A monitoring apparatus includes a wearable electronic device having an audio port and a headset having at least one earbud, at least one physiological and/or environmental sensor, and circuitry that processes signals produced by the at least one physiological and/or environmental sensor and transmits the processed signals to the electronic device via the audio port. The headset may include a microphone in audio communication with the electronic device via the audio port, and the circuitry modulates audio signals produced by the microphone and signals produced by the at least one physiological and/or environmental sensor for transmission to the electronic device via the audio port. The circuitry may power the at least one physiological and/or environmental sensor via power supplied by the electronic device through the audio port and may include a processor that coordinates collection, modulation, and/or transmission of signals produced by the at least one physiological and/or environmental sensor.