A closed loop system is disclosed for monitoring patient movements, such as tremors, and for automatically controlling an implantable stimulator device on the basis of the detected movements. The system includes a motion sensor such as a wearable item that contains an accelerometer to monitor a patient's movements, such as a ring locatable proximate to a patient's hand tremor. The motion sensor periodically transmits a feedback signal to the implantable stimulator device instructing it to change the stimulation parameters, such as current amplitude, in an attempt to reduce the tremor. The motion sensor can additionally communicate with other system components such as an external controller. In a preferred embodiment, the motion sensor and the implantable stimulator device communicate using short range electromagnetic radio waves.