Your watch already knows you’re stressed.

Vayu is a real-time biofeedback breathing app. It reads heart rate variability (HRV) from Apple Watch and Wear OS devices and guides your breath through wrist haptics the moment stress is detected, with no screen and no sound. Vayu supports 68+ smartwatch models and is used by 55,000+ people, with 64% Day-30 retention (2.5× category average).

Calm and Headspace play audio content through your phone. Vayu reads your physiology through your watch and responds to it in real time. Calm plays a track when you open the app; Vayu intervenes when your nervous system is dysregulated, even while your phone stays in your pocket. Vayu measures HRV live during every session. Calm has no HRV integration.

Vayu reads real-time heart rate variability from Apple Watch during breathing sessions. As you breathe, your HRV changes. Vayu tracks this live and paces your breath through haptic taps on your wrist. You can watch your HRV improve in real time on the watch face, and your phone never has to leave your pocket.

Box breathing (4:4:4:4), resonance frequency breathing (5 to 6 breaths per minute), 4-7-8 breathing, the Wim Hof method, and custom breath ratios. Every technique is available with haptic guidance on Apple Watch and Wear OS, with real-time HRV feedback during the session.

Resonance frequency breathing synchronizes your breath with your heart rhythm to maximize heart rate variability. The optimal rate is typically 5 to 6 breaths per minute, roughly five seconds in and five seconds out, though it varies by individual. Vayu measures your personal resonance frequency from your HRV response and adapts its guidance accordingly.

Yes. Your Apple Watch or Wear OS device guides your breath through wrist haptics and tracks your HRV on its own. You never need to look at a screen during a session.

HRV is the variation in time between consecutive heartbeats, measured in milliseconds. Higher HRV indicates an adaptable, well-recovered nervous system; lower HRV is associated with stress, fatigue, and overtraining. Vayu measures RMSSD, the standard clinical metric for short-term HRV.

Yes. Vayu runs on Android phones and Wear OS watches, including Pixel Watch, Samsung Galaxy Watch, and 68+ smartwatch models in total. The iOS version supports iPhone and Apple Watch. Both include real-time HRV biofeedback and haptic guidance.