Sthenos
A live 0-100 energy score from your Apple Watch, computed entirely on your device.
Today 
Trends 
Vitals 
The science
About
Sthenos turns Apple Health data into a single running energy level. You recharge during rest and sleep, when your heart rate settles and your HRV rises, and you drain through activity, an elevated heart rate and physiological stress. Recent hard training keeps weighing on the score for days.
Everything is judged against your own baseline, which Sthenos learns over about two weeks, rather than population averages. The score sits in a heart gauge that fills and empties, with the four factors behind it (sleep, recovery, heart and freshness) one tap away.
Health data is read from Apple Health and processed locally. There is no account, no tracking and no server, and nothing is written back to Health. Sthenos is a personal wellness tool, not a medical device.
Features
Live energy score
A 0-100 number in a heart gauge, with a read on whether you are charging or draining right now.
Four score factors
Sleep, recovery, heart and freshness, each with a plain-English explanation for today.
Trends and training load
Score history over days to months, plus fitness, fatigue and form from your workouts.
Vitals against your normal
HRV, resting heart rate, blood oxygen, VO2 max, sleep and more, each shown against your own range.
Apple Watch app
Score, factors, vitals and training load on the wrist, with watch-face complications.
Home Screen widgets
A score widget and two configurable Vitals widgets where you choose every metric.
On-device AI insights
A short written read on your day, generated locally with Apple Intelligence.
Private by design
No account, no ads and no servers; health data never leaves your iPhone.
Pricing
One-time purchase
- SthenosPaid app; the listing shows no in-app purchases$3.99
Prices as listed on the US App Store (checked October 2026); they vary by region.