Amazing - thanks! And for respiratory rate, are you just taking the chest rise and fall from the accelerometer? Would it be obscured by general x,y,z body movement or are you filtering it in some way?

It actually looks much smoother than the trace we get from respiratory inductance plethysmography...

Yes basically, I remove the gravity component by high pass filtering, and then take just the component of acceleration which is along the axis of chest expansion (i.e. pointing out from the sensor) off the top of my head this is the z axis. But this only works when you are sitting quite still, movement introduces a lot of noise to the acceleration