Most standard tattoo ink colors are derived from heavy metals, including antimony, beryllium, lead, cobalt-nickel, chromium, and arsenic. Other additives include surfactants, binding agents, fillers, and preservatives. Obviously the metals then block the sensors from direct contact with your skin as if you have an extra layer.
As for the no notification when not being worn is probably to safe battery life and if charging it probably helps to charge faster and Keep the watch cooler. I hope this helps?
