A physiological characteristic monitoring system includes a physiological characteristic sensor that observes a physiological characteristic and generates sensor signals based on the observation. The physiological characteristic sensor includes a sensor connector. The physiological characteristic monitoring system includes a wearable device to be worn by a user in a first configuration and having a connector to couple to the sensor connector in a second configuration. The wearable device includes a controller that receives the sensor signals from the physiological characteristic sensor in the second configuration and determines a current value of the physiological characteristic based on the sensor signals.