A servo makes a great instrumented gearmotor for greater control. The Servo Based Gearmotor is a hacked HS-311 with 51 oz-in of torque. The electronics have been removed and leads added to control the motor directly. The servo lead is now connected directly to the potentiometer. Works great with our Cortex: Robot Arm Controller! (https://www.etsy.com/listing/271308603/cortex-robot-arm-controller) Note this motor requires a speed controller or motor driver.