Helix does not require an Apple Watch, and it will not pretend one is on your wrist. This page is the honest capability matrix: what each part of the app does with a watch, what it does with only an iPhone, and where the line comes from.
The principle: honest numbers
One rule decides every row of the table below: Helix never invents a value it didn’t measure. If a signal is missing, it shows as missing. If a number is estimated, it is labeled as an estimate. A day of strain with no heart-rate data shows a dash and asks for the watch, because a fabricated strain number would be worse than none. That rule costs Helix some impressive-looking screens on phone-only setups, and it is the reason you can trust the screens you do get.
The capability matrix
| Area | With Apple Watch | iPhone only |
|---|---|---|
| Recovery | Full: overnight HRV, resting heart rate, respiratory rate, SpO₂ and wrist temperature feed the morning score | Limited: the overnight vitals are missing, so the score leans on what the phone can see and says so |
| Strain | Full: all-day load plus live strain climbing during workouts | Needs real heart-rate presence; no fabricated values. Days without heart-rate data show a dash, not a guess |
| Sleep | Stages, efficiency, latency, debt and regularity | Duration and timing from iPhone motion detection, honestly labeled as an estimate; no stages |
| Stress | Realtime signal from heart rate and HRV through the day | Not available; it needs watch heart-rate data |
| VO₂max | Trajectory from watch-recorded workouts, plus the Cooper test and guided intervals | Not available; it needs watch workouts |
What phone-only users still get
Plenty of Helix does not depend on the wrist at all, and none of it is watered down on a phone:
- The sleep-anchored day. Phone-estimated sleep still gives Helix your wake time, so your day rolls over when you actually wake, not at midnight. See the sleep-anchored day.
- Sleep duration and timing, clearly labeled as estimates, which is enough for sleep debt and regularity to mean something.
- Nutrition logging by photo, barcode or text.
- Bloodwork: panel uploads and marker scoring have nothing to do with a watch.
- Trends and the journal, built from whatever data you do record.
Which watch?
Any Apple Watch that records overnight vitals works. Wear it to sleep and Helix gets the HRV, resting heart rate and respiratory rate that recovery is built on, plus real heart-rate presence for strain and stress. Newer models add wrist temperature, which gives the recovery score one more overnight signal to baseline. There is no Helix-specific hardware requirement beyond that: the app is built to run on the watch you already own, not to sell you a new one.
If you are setting up now, install & permissions covers granting Health access, and your first morning covers what the first tracked night unlocks. For the wrist app itself, complications and live workout tracking, see the watch app.