Supported Features
-
Dark Interface
-
Differentiate Without Color Alone
-
Sufficient Contrast
Vagal HRV: Guided Breathing
Polar H10 & cardiac coherence
Only for iPhone
Free · Designed for iPhone. Not verified for macOS.
iPhone
Vagal HRV measures heart rate variability (HRV) with chest-strap accuracy and trains your breathing with real-time biofeedback.
FREE, NO SUBSCRIPTION
No ads, no mandatory account, no hidden paid tier. Everything below is available from the first time you open the app.
START WITH NO SENSOR AT ALL
Guided breathing runs on the phone alone: pick a protocol (Coherence 6, Box 4-4-4-4, Relax 4-7-8, extended exhale), follow the pulsing circle, done. No strap, no account, no subscription.
When you want to measure your HRV, that's when the Polar H10 comes in.
KEY FEATURES
• Guided breathing — a pulsing circle and soft tones in 4 phases, with ready-made protocols. Works with no sensor.
• Quality-checked HRV — RMSSD, SDNN and max/mean/min heart rate from the Polar H10's true RR intervals, with artefact correction and a quality score on every reading.
• Readiness — a score compared with your own baseline, with a green/amber/red light.
• Cardiac coherence — see live how large your heart rate swing gets while you breathe slowly.
• Coherence training — a daily program with a streak and a goal that grows weekly.
• Resonance finder — sweeps 4.5 to 6.5 breaths per minute and shows which pace produces the largest heart rate swing.
• Context tags — log sleep, alcohol, training and stress, and see how each one shows up in your own history.
• Trends and history — 7 and 30-day averages, best time of day, CSV and PDF export.
• 6 languages, light and dark themes.
WHY A CHEST STRAP?
Watches and rings estimate heart rate from light (PPG). The Polar H10 is a chest strap that measures beat-to-beat intervals directly, the gold standard for HRV — far more reliable RMSSD and SDNN.
POLAR H10 SENSOR REQUIRED FOR HRV
This app does not collect HRV from the iPhone itself. Measurement requires a Polar H10 chest strap, sold separately by Polar, connected over Bluetooth. Guided breathing needs no sensor.
PRIVACY
Your data stays on your device. We do not send your measurements to any server. You decide when to export or share.
IMPORTANT NOTICE
Vagal HRV is for wellness and sporting purposes only. It is not a medical device, does not perform electrocardiography, and does not diagnose, treat or prevent any disease. Always consult a physician before making decisions about your health.
Polar and Polar H10 are trademarks of Polar Electro Oy. This app is not affiliated with Polar Electro Oy.
Ratings & Reviews
- This app hasn’t received enough ratings or reviews to display an overview.
Now you choose how to start: breathing only, with no equipment at all, or breathing plus HRV measurement with a chest strap.
• Voice-guided breathing, female or male, in the app's language
• Sound options: voice, tone or silent
• Your resonance rhythm, once measured, becomes a breathing protocol
• Cleaner home screen that no longer asks for a sensor you don't use
The developer, Cristiana Kaleff, indicated that the app’s privacy practices may include handling of data as described below. For more information, see the developer’s privacy policy .
Data Not Collected
The developer does not collect any data from this app.
The developer indicated that this app supports the following accessibility features. Learn More
Information
- Seller
- Cristiana Kaleff
- Size
- 24 MB
- Category
- Health & Fitness
- Compatibility
Requires iOS 15.0 or later.
- iPhone
Requires iOS 15.0 or later. - iPod touch
Requires iOS 15.0 or later. - Mac
Requires macOS 12.0 or later and a Mac with Apple M1 chip or later. - Apple Vision
Requires visionOS 1.0 or later.
- iPhone
- Languages
- English
- Age Rating
9+
- 9+
- Contains
Health or Wellness Topics
- Copyright
- © 2026 AK BioSystems