A system comprising: a wrist-worn device configured to be worn on the wrist of a rescuer performing cardiopulmonary resuscitation (CPR), the wrist-worn device including: one or more sensors coupled with the wrist-worn device, the one or more sensors being configured to sense one or more parameters indicative of a fatigue level of the rescuer; and a sensor interface configured to provide the sensed parameters to one or more external computing devices via an interface; and a wearable computing device configured to be worn by a rescuer, the wearable computing device including: a device interface for receiving information related to CPR; and a display for displaying an indication of the received information.