What's new in this patent? Cheap ($10) pulse ox sensors operating on similar principles have been available since well before this patent has been filed.
There are hundreds of companies making wearable SpO2 monitors. Hell, I worked for one. Ours were transmissive, whereas I'm pretty sure most wearables are reflective. Maybe that's the key, who knows.
What do you meant by transmissive wearable, for fingers normally it is fine that you have in-situ measurement settings, for wearable like smart watch it will be clunky to have transmitter and receiver at the opposite of sides of (relatively massive) hand?
Earlier iterations of the design weren't as chunky as what they're doing now.
PPG readers are tiny, they could easily fit in a watch wrist strap with a little cable connecting back to the main assembly. The hard part would be making sure the sensor is aligned with the LED.
I could imagine transmissive at the belly button to work out with decent design effort, or maybe around the ear.
Nostrils seem unlikely to be comfortable, but would probably work fine.
