I would wish that on a new watch, the sensors that measure blood oxygen, they have to be between the two bones in the arm , the radius and ulna, for it to work. Should the area be too narrow, the sensors do not work. However, the heart rate sensors do not seem to be bothered by the location . The wish is that the either narrow the distance between the sensors or move the orientation of the sensors to make that reading.
IF they go the same theory or route on blood glucose, this will be a problem. What I am guessing is that the watch won't measure the BG reading, but relay it from some sensor imbedded in the skin, such as Dexcom6 or Freestyle. Those sensors come off, cost over 300$ a month and medicare only laughs when someone asks if they cover it.
Who knows, I will wait for Watch 8.