The sensors on an Apple Watch are fine for tracking breath while you're absolutely still. That's how devices like https://nightware.com/ https://nightware.com/

The sensors on an Apple Watch are fine for tracking breath while you're absolutely still. That's how devices like https://nightware.com/ https://nightware.com/ can work. What's a device like the Apple Watch can't do is track breath on someone who is standing up and moving around.