For what purpose? If you just want to know your respiratory rate, respiration belts are simple and very effective. You should be able to MacGyver your own with

For what purpose? If you just want to know your respiratory rate, respiration belts are simple and very effective. You should be able to MacGyver your own with limited electronics skills: https://www.instructables.com/Quick-and-dirty-Respiration-Sensor/ https://www.instructables.com/Quick-and-dirty-Respiration-Se.... > To what extent is a microphone in your glasses + footage of your chest rising and falling enough? I'm sure a skilled computer vision engineer could make this work, but I'd argue it's the wrong approach. Lasers might work as well, but I think your best bet is radar. I know there are companies making doppler radar-based systems for tracking respiratory rate. Can't dig for them at the moment but here's an article about the method: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10172641/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10172641/. By the way, heart-rate variability correlates strongly with respiratory rate. As far as I understand, this is because inhalation raises your blood pressure which increases your heart rate. Using a pulse oxymeter, you should be able to extract respiratory rate from the raw PPG data. Should be effective if you're otherwise healthy and reasonably young. HRV decreases with age and illness. https://pubmed.ncbi.nlm.nih.gov/34024811/ https://pubmed.ncbi.nlm.nih.gov/34024811/