A monitoring system that can be placed proximate to the head or ear of a user is disclosed. According to one embodiment, the monitoring system can be used with headphones, earbuds or headsets. The monitoring system can, for example, be used to monitor user activity, such as during exercise or sporting activities. The positioning of the monitoring system can also facilitate sensing of other user characteristics (e.g., biometric data), such as temperature, perspiration and heart rate. The monitoring system can also be used to control a an electronic device. In one embodiment, the monitoring system facilitates user control of the electronic device using head gestures.