Health data is some of the most personal data you have. It can show when you are ill, how you sleep, how much you drink and what medication you take. We think the safest place for it is the device that recorded it. So Metrya was designed from the start so that your health data doesn't need to leave your iPhone.
What Happens on Your iPhone
All the calculations run on the phone:
- Recovery, Reserve and sleep debt
- Sentinel and Recovery debt
- The Stress Monitor
- Training load, zones and the daily training suggestion
- Weekly reports, blood pressure and biological age
- Notifications: built on the phone from your numbers, not pushed from a server
There is no sign-up. No email, no password, no user ID on a server. The Apple Watch app talks only to your iPhone and to Apple Health on the watch.
The AI Advisor: You Choose Where It Runs
The Advisor is optional, and on a new install it starts turned off. Nothing about your health reaches any AI model until you turn it on. When you do, you pick one of three options:
You see what is sent before it is sent
Before your health data goes to a cloud provider for the first time, Metrya shows you the actual request: which metrics, which dates, what the instructions say, and the full payload if you want it. Agreeing for one provider doesn't agree for another. After that:
- Every message says where it is going before you send it: the provider by name and how many health fields are attached, or that it stays on the device.
- Never included: your name, email, Apple Health identifiers, device ID or location.
- Prompts, health data and answers are not written to logs.
- Scheduled AI reports check your permission when they run. Turn the Advisor off and nothing is generated.
- One screen lets you turn the Advisor off, remove API keys, or delete every AI chat, memory and report stored on the phone.
Read more about keys and costs on the BYOK page.
What Goes Online, and Why
"Nothing ever touches the internet" would not be true, and we'd rather be exact. These are the things that do go online. None of them contain health data.
| What | What is sent | To whom |
|---|---|---|
| Weather, air quality, pollen | A coarse location, rounded to about 1 km | Metrya's environment service |
| Food search and barcodes | Your search words or the barcode number | Open Food Facts, directly |
| Research library | A request for new studies. The "For you" list is worked out on the phone. | Metrya's research service |
| Purchases | What Apple's in-app purchase system needs | Apple and the purchase service |
| Feedback | Only the text you choose to send | Metrya |
| Cloud AI (optional) | The health data for your question, after you've seen it | The provider you chose, with your key |
Why We Built It This Way
Two reasons. The first is trust: you shouldn't have to trust a company's servers with data that says this much about you. The second is practical. If we don't store health data, it can't leak from us, be sold, or be handed over. And because there are no servers doing the work, Metrya can be sold as a one-time purchase instead of a subscription.
What Apple Health Access Means
When you allow Apple Health, you choose which categories Metrya can read. Metrya only writes back what you log in the app, such as meals, water, blood pressure entered by hand and sauna or cold-plunge sessions. You can change access at any time in the iPhone Settings app. Allowing Apple Health never means allowing AI: those are separate choices.
Limits We Want You to Know About
- A cloud AI provider receives what you send it. Once a request reaches Anthropic, OpenAI or Google, their own policies apply. If that matters to you, use Apple Intelligence or a model on the phone.
- Your phone is only as safe as its passcode. Health data on an unlocked phone is readable by whoever holds it.
- Other apps have their own rules. Data you share with other apps through Apple Health follows their policies, not ours.
The full legal text is in the privacy policy.
Your data, on your phone.
Download Metrya, allow Apple Health and see your recovery, sleep and energy, all calculated on your iPhone. No account needed.
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