This is the openEMSstim, a hardware board based on an Arduino Nano that modulates the amplitude of Electrical Muscle Stimulation (EMS) signals. Here you also find the software that communicates with the board and controls it (android, unity, etc). This board is controllable via Bluetooth and compatible with any BLE device you have (such as your smartphone). It also is controllable via Serial (USB) by plugging in a USB cable from your computer to the Arduino Nano on the board. All the necessary information for getting started is compiled in a step-by-step tutorial, start here.