Here is a simple, low-cost, high quality servo for all your mechatronic needs. This servo is very similar in size and specifications to the Hitec HS-55. This little guy is able to take in 6 volts and deliver 20.8 oz-in. of maximum torque at 0.10 sec/60°
The Pololu 4-Channel RC Servo Multiplexer can be used with standard hobby radio control systems and servo controllers to allow easy switching of servo control between two independent sources using a separate auxiliary channel as the input selector.