As a physiologist who normally does not code:
as far as I can judge, the easiest way for a real-time respiration monitor is the following path with the following components:
1. Jukka Happonens Polar Sensor Logger app with MQTT
2. Receive MQTT stream in Matlab (although I am against using Matlab for this project)
3. Connect it to Peter H. Charltons Respiratory Rate Estimation Toolbox for Matlab in real-time
4. port the software to Octave:
https://forum.sierrawireless.com/t/mqtt-on-octave/23657
5. Validate it with a Quark CPET, as Swiss researchers did with the Polar H10:
https://www.cosmed.com/en/products/cardio-pulmonary-exercise-test/quark-cpet
Do it for fun and in your spare time, develop an app or a Python Toolbox from scratch, write a paper or sell a product.
24.3.22 17:05
For all non-coders, I suggest not to use a real-time device. The only consumer grade real-time respiration monitor I know which is comfortable to wear is sold by Garmin (Firstbeat), which is not a solution which is satisfying for me personally:
25.3.22
MQTT interface for Octave/MatLab/Simulink: