A small, rugged electronics and sensor package will be developed that will be installed within the housing of the Constant Speed Drive (CSD). The Variable Reluctance sensor that is used will monitor the tooth-passing speed of an existing input shaft gear. The micro-controller within the electronics package will count the revolutions and correlate the revolutions with statistics such as input shaft speed and internal temperature. Communication with the electronics will be facilitated through existing connectors and will be accomplished without disassembling the CSD. A novel energy harvesting method will be used to power the electronics from the variable reluctance sensor, allowing for a long service life.The data collected can be expanded to include hydraulic oil condition, temperature, pressure, vibration, and other metrics to provide insight into CSD operating conditions. All these sensor modalities are familiar to KCF since we offer them as a part of our commercial sensor suite for monitoring heavy industrial equipment like motors, gearboxes, pumps, compressors, and robotics. KCF Technologies is a leader in industrial prognostic health monitoring which can be leveraged to enable the Input Shaft Monitor to predict failures. This capability would allow for scheduled repairs and CSD damage prevention.