My Dad has high blood pressure and when he wants to check his blood pressure, he needs a second person to help him, because when you are taking blood pressure, you need to pump up the arm restriction. For the blood pressure gauge to work, you need to hold the stethoscope in place so that you can tell when the blood has stopped and when it is circulating again. As one arm is being obstructed, it is difficult to inflate the restriction with one hand and hold the stethoscope in the other. It was also inconvenient to call a second person. This is why I made a device that could be clipped onto the finger so that the pulse could be displayed on an oscilloscope without using a stethoscope.