A system can be used to indicate wear of a brake pad. The system can include a brake housing, a brake pad mechanically coupled to the brake housing, and a sensor mechanically coupled to the brake pad. The sensor can determine when the brake pad has been worn to a predetermined location by a rotating portion of a wheel. The system can also include an electronic module electrically coupled to the sensor and mechanically coupled to the brake housing. The electronic module can include a radio frequency antenna configured to wirelessly receive radio frequency energy from an external radio frequency transmitter, and an energy converter electrically coupled to the radio frequency antenna. The electronic module can include an internal transmitter electrically coupled to the energy converter and the radio frequency antenna.