The current tech wouldn’t fit into a watch, but they’re working on new tech to do these, mostly based on using lights/lasers that are already in the watch.

And the FDA doesn’t care how you build it, just that it works. It’s easier if you copy an existing technology because the FDA clearance is easier, but the hurdle isn’t very high for new tech in this relatively simple area, i.e., did our devices readings match the gold standard reading?

The taxes and fees are not on the $10. Wait for your second month’s bill.