Heart stress · recovery companion

Beyond steps —
read your heart.

A daily Heart Stress Index (HSI) and recovery guidance, built from HRV, resting heart rate and overnight signals in Apple Health — all computed on your iPhone.

Get it on the App Store How HSI works

iOS 26 · Apple Watch recommended

HealthKit · HRV steady

Four tiers

Compared to your baseline, not anyone else's

HSI is calibrated against your personal 28-day distribution and grouped into four tiers from 0 to 100. The trend and reasons matter more than the absolute number.

0 – 24

Recovered

HRV is full, overnight HR is low, sleep is complete. A great day for training or pacing.

25 – 49

Steady

Within your baseline range. Keep your routine, hydrate and consider a short nap.

50 – 74

Watch

Overnight HR is elevated or HRV is sliding. Dial back intensity and protect sleep.

75 – 100

Overloaded

Multiple signals are off baseline. Take a recovery day and consult a doctor if symptoms persist.

Product tour

Understand yourself in 3 seconds a day

Today, long-term trends, sleep and activity — four core screens that make up your recovery picture.

Today

MaiBao plus your heart-stress score — current state at a glance.
Trends

Weekly / monthly / yearly stress distribution, long-term change made clear.
Sleep detail

Sleep score broken down by duration, deep sleep and awakenings.
Activity

Move / Exercise / Stand rings plus daily steps.

Core features

See the score — and understand your body

From daily heart stress to sleep, trends, risk and a doctor-ready summary — all computed on-device from Apple Health.

Daily Heart Stress Index

A 0–100 score across four tiers, calibrated to your own 60-day rolling baseline (median + MAD) — not a global average. Falls back gracefully when data is thin (Tier S / B), powered by the transparent CSS v3.2 algorithm.

0 100

Root-cause breakdown

See how much HRV, resting and overnight HR, sleep, respiration and activity load each contributed — ranked by impact, so today's score makes sense.

Trends & heatmap

Week / month / year trends, HRV and resting-HR curves, stress distribution, plus a calendar heatmap and 24-hour intraday heart load.

Sleep analysis

Sleep-stage timeline, quality score, heart-rate dip and REM ratio — layered with overnight respiration, SpO₂ and wrist temperature.

Risk alerts & push

Get notified on sustained high stress, under-recovery or anomalous days linked to symptoms — toggle anytime in Settings.

Symptom logging

One-tap log for palpitations, chest tightness, dizziness, late nights, alcohol or caffeine — correlated with that day's heart data.

Doctor-ready PDF

Week / month / custom periods exported as a multi-page PDF of trends, key metrics, triggers and symptoms — take it straight to your physician.

MaiBao · Widgets · Apple Watch

A plush heart that shifts expression with your state, with four home-screen widget sizes and an Apple Watch view — your status at a glance.

MaiBao · 脉宝

A heart-shaped friend, beyond the numbers

MaiBao shifts through four moods to mirror your state. It's easier to act on a friend than on a number.

Recovered

"I'm feeling great today."

Steady

"Cruising — keep it up."

Watch

"A little tired. Early night?"

Overloaded

"Let's take it easy today."

FAQ

Things you might be wondering

Is HeartStress a medical device?

No. HeartStress is a trend-monitoring and recovery companion. It does not predict or diagnose cardiac events. If you experience persistent discomfort, consult a healthcare professional.

Do I need an Apple Watch?

Strongly recommended. HRV and overnight HR come primarily from Apple Watch. iPhone-only falls back to an RHR-only model with reduced precision.

Is any of my data uploaded?

No. Every calculation runs locally on your iPhone using Apple HealthKit. Persisted state is encrypted by iOS. There is no server.

Which signals does the HSI algorithm use?

Overnight HR, HRV, RHR, sleep efficiency and duration, and activity load. The CSS v3 algorithm is three-layered: sub-scores → guardrails + trend → composite.

Is there a trial for Pro?

Yes. Both monthly and yearly plans include a 7-day free trial. Cancel a day before renewal at no charge.