Above-elbow myoprostheses aim to restore the functionality of amputated limbs and improve the quality of life of amputees. By using electromyography electrodes attached to the surface of the skin, amputees are able to control motors in myoprostheses by voluntarily contracting the muscles of their residual limb. An advance in myoelectric control called targeted muscle reinnervation (TMR) reinnervates severed nerves into healthy muscle tissue and increases the number of muscle sites available for use in control purposes. In order to improve rehabilitation after TMR surgery, an inexpensive myoelectric training tool has been developed in collaboration with the Glenrose Rehabilitation Hospital that can be used by TMR patients for biofeedback applications. The training tool consists of a robotic arm, signal acquisition hardware, controller software, and a graphical user interface. This dissertation describes the design and evaluation of the training tool and its use as a research platform for testing novel controllers.