The control of a myoelectric prosthesis requires extensive rehabilitative training based on repetitive exercises. But at home, many patients lack the motivation to continue the physiotherapy exercises. Mobile games on a smartphone can contribute to a long-term motivation to continue home training with the necessary intensity. The patients control the game with their muscle signals, exactly how they would control their actual prosthesis. In this study, we examined the usability of the gaming system, its functionality and subjective quality. It was rated highly in all aspects by both experimental groups, with the patient group consistently rating higher than the able-bodied group. Although highly rated, results showed detailed potential for improvement regarding the aesthetics of the app and provided information in-app. The mobile training app not only provides feedback on the correct execution of muscle activation, but also maintains the patient’s motivation through various feedback elements. In a clinical pilot study, three upper limb amputees trained their neuromuscular control over the course of four weeks while playing the game and clinical parameters important for prosthetic control have been evaluated pre and post intervention. Significant improvements could be seen in all assessed parameters which supports the thesis that a game-based mobile app can be used to train EMG motor signals for prosthetic control.