Technology for a wearable heart rate monitoring device is disclosed. The wearable heart rate monitoring device can include a heart rate sensor operable to collect sensor data, a modulator operable to generate a modulated signal that includes the sensor data, a housing configured to engage a body feature or surface in a manner that allows for heart rate detection, and a communication module configured to transmit the sensor data in the modulated signal to a mobile computing device via a wired connection that is power limited. The mobile computing device is typically configured to demodulate the modulated signal in order to extract the sensor data.