First of all, the MyoWare Muscle Sensor can be connected to an Arduino, and the Arduino connected to a laptop (which is not connected to the mains electrical grid). So, we can see the data acquired from EMG in real-time, using serial monitor (see https://www.arduino.cc/reference/en/language/functions/analog-io/analogread/ )

void setup() {
Serial.begin(9600);
}

void loop() {
Serial.println(analogRead(pin));
}