You're wearing it wrong
I wear my watch on the inside of my wrist to prevent me constantly banging it on door frames and stuff. I don't know about you but the inside of my wrist is definitely not hairy, and the sensors would work just fine.
I wear my watch on the inside of my wrist to prevent me constantly banging it on door frames and stuff. I don't know about you but the inside of my wrist is definitely not hairy, and the sensors would work just fine.