[runnerup]

I have to read into this answer a lot. Would it be accurate to say that the app calculates a "target" respiration rate, then provides visible or audible cues (e.g. a metronome) to tell the user exactly when to inhale/exhale? So the "actual" respiration isn't measured, but that isn't very important as it's quite trivial for a user to follow "inhale now", "exhale now" cues to the necessary degree of precision.

Did I understand that correctly?

[tamadevr]

Yes that’s essentially it. We calculate your target/ideal breathing rate and then have breathing guides during the session for you to follow. Then you’re able to see your heart rate graph in realtime and understand how it changes with your breathing.