Disclosed herein is a shaft-mounted monitor for monitoring conditions of a rotating shaft using a calculated rotational component of the rotating shaft. The monitor may include a sensor such as an accelerometer, thermal sensor, strain gauge, or the like. In various embodiments, a variety of parameters relating to the rotating shaft may be monitored, such as a temperature, rotational speed, angular position, torque, power, frequency, or the like. The monitor may include a wireless transmitter to transmit the monitored condition of the rotating shaft to an intelligent electronic device or a monitoring system.