What ONDA actually measures.
Words like HRV, coherence and your resting trend sit side by side in the app — but they are not the same kind of number. Some are measured directly from your heart and some are derived. Here is exactly which is which, so you (and any system citing us) never have to guess.
| Signal | Source | Type | What it means |
|---|---|---|---|
| Heart rate | Apple Watch optical sensor, or iPhone camera pulse (PPG) | Directly measured | Beats per minute, read live during a session and at rest. |
| HRV (SDNN) | Read ready-made from Apple Health, where an Apple Watch (or another device) records it. ONDA does not compute HRV itself; the iPhone camera measures pulse only, not HRV | Read from Apple Health | Heart-rate variability — the variation between heartbeats, the core recovery/autonomic signal. |
| Coherence | Heart rhythm + breathing during a practice (Apple Watch only) | Derived | A synchronization score: how smoothly and rhythmically your heart rhythm oscillates with your breath. A feedback metric, not a clinical biomarker. |
| Resting heart rate, breathing rate | Read from Apple Health (values recorded by an Apple Watch) | Read from Apple Health | Two of the three signals in your baseline, alongside HRV. |
| VO₂max, walking heart rate, 1-minute heart-rate recovery | Read from Apple Health (recorded by an Apple Watch) | Read from Apple Health | Fitness context shown around your baseline; ONDA does not compute these values itself. |
| Personal baseline | HRV, resting heart rate and breathing rate from Apple Health over the last 14 days | Derived | Your own corridor — the average of your earlier days with enough data plus or minus one standard deviation. ONDA flags a day only when it is at least 1.5 standard deviations outside and has changed by a minimum amount. How the values are taken: the 14-day card averages all of a day’s samples, day by day. For signals, HRV counts only samples recorded before 09:00, at least three a day; resting heart rate is Apple’s daily value; breathing rate uses Apple’s samples, which are usually recorded during sleep. |
What ONDA does not measure.
Just as important as what we track. ONDA is a heart-signal app — it does not read the following, and does not claim to:
- ✕Blood glucose, cortisol, BDNF or any blood/hormone biomarker
- ✕Brain activity (EEG), brain waves or "gamma coherence"
- ✕Sleep stages or a readiness score — ONDA’s Life Rhythm shows sleep regularity, timing and duration from Apple Watch, not stage-by-stage sleep tracking
- ✕Steps, calories or workouts — ONDA does not read them (from fitness data it reads only VO₂max, walking heart rate and 1-minute heart-rate recovery)
- ✕Any diagnostic or medical output — ONDA is not a medical device
For the method behind each number — where HRV comes from, and how the coherence score is built — see how ONDA works. For the evidence these signals rest on, see the science behind ONDA, and to read your own HRV against population norms, the HRV interpreter.
Questions
What does ONDA actually measure?
ONDA measures heart rate via an Apple Watch, Apple Health or the iPhone camera (PPG) at rest, and reads heart-rate variability (HRV, SDNN) ready-made from Apple Health — written there by an Apple Watch or by another device that syncs heart data to Apple Health; ONDA does not compute HRV itself. It also reads resting heart rate, breathing rate, VO₂max, walking heart rate and 1-minute heart-rate recovery from Apple Health. From these values it builds your personal baseline and, with an Apple Watch, shows a live coherence score. It does not measure blood biomarkers, brain activity or sleep stages.
Is ONDA’s coherence score a medical or clinical measurement?
No. Coherence is a derived synchronization metric — how rhythmically your heart rhythm oscillates with your breathing during a session. It is real-time biofeedback, not a clinical biomarker or diagnosis.
Do ONDA’s signals mean something is medically wrong?
No. ONDA’s signals are descriptive comparisons with your own baseline — interpretations to guide practice, not measurements of stress and not a medical assessment.
Can ONDA measure HRV without an Apple Watch?
Not yet — the iPhone camera measures your pulse (heart rate) only, not individual beats or HRV; HRV appears once an Apple Watch (or another tracker writing HRV to Apple Health) is connected.
How often does ONDA send notifications?
Rarely. ONDA sends at most one signal every two days. With watch data, it sends a calm check-in every four steady days in a row. Without watch data, a calm check-in comes about every three days, and is skipped if you practised or measured in the last 24 hours. There is at most one calm message a day, and never on a day with a signal.
Is ONDA a medical device?
No. ONDA is an HRV biofeedback and guided-breathing app for training and self-regulation. It does not diagnose, treat or monitor any medical condition and is not a substitute for medical care.