Privacy Policy

The short version

• Your body data never leaves your iPhone. Your weight, height, BMI, measurements and check-in answers stay in the app’s own storage on your device.
• There is no account and no server of ours. No sign-up, no password, nothing for us to look up.
• The only thing we collect is anonymous usage and purchase events — which screens you opened and how purchases went. It is tied to a random device id, not to you.
• You can switch that off in two taps in Settings → Data and privacy.
• Apple Health data is never sent anywhere. Not to us, not to our analytics provider, not to anyone.
• No ads, no tracking, and nothing sold or shared for anyone else’s marketing.

1. Who we are

This app is made by Resonance Logic, LLC, a software studio in New York. The app is BMI Calculator: Weight Plan (“BMI Plan”) for iPhone. This policy covers that app.

You can reach us at bmi@resonance-logic.com.

2. There is no account and no server of ours

The app has no sign-up, no login, no password and no user profile on any machine we own.

Everything you enter is written to a database inside the app’s own container on your device: your profile, measurements, calculator results, lesson progress, check-in answers, habit tracking, food and drink logs, quiz answers and feature settings.

We cannot read it, and we cannot recover it. Deleting the app deletes it.

3. Apple Health (HealthKit)

Apple Health is optional. The app asks for it separately from everything else, and it works fully without it.

• Reads: your body weight — so your trend line updates when a smart scale writes to Health.
• Writes: your weigh-ins and BMI — so your other apps stay in sync.

Health data is never sent to us, to our analytics provider, or to any third party. It is never used for advertising. It is read and written on your device only.

You can revoke access at any time in iOS Settings → Health → Data Access & Devices.

4. The health questions we deliberately do not keep

Your answers about pregnancy, breastfeeding, and cardiac or exercise clearance are held in memory for the length of that session only. They are never written to the database and never leave the device.

Those answers only ever remove a suggestion. They never select one, and they never produce a diagnosis.

5. Anonymous usage analytics — the one thing we do collect

We use PostHog (US cloud, us.i.posthog.com) to see which parts of the app people use and where purchases go wrong.

Who it says you are

An anonymous, randomly generated device id. We never identify you to PostHog. There is no name, no email, no account, and nothing to join it to.

What is sent

• Which screens you opened.
• The outcome of purchase steps: the product identifier, the store’s own displayed price and currency, the offering or package identifier, whether a free trial applied and how long it was, which screen the purchase started from, and whether a purchase is a trial or set to renew.

What is never sent — enforced in code

Before any event leaves your device, every property name is scanned word by word against a denylist. Weight, height, BMI, body fat, waist, neck and hip measurements, age, date of birth, sex, calorie targets, pregnancy, breastfeeding, clearance, conditions, symptoms, diagnoses, injuries, names, emails, phone numbers, addresses and IP are all dropped. Any free-text string longer than 64 characters is dropped as well.

What we deliberately turned off

• Autocapture is off. Left on, it would have sent the exact text of the health questions.
• Session replay is off.
• Surveys and remote feature flags are off.
• Push-notification capture is off.
• IP-based geolocation is off.
• Your device’s own name, your IP address and your raw user agent are stripped out.

No advertising, no tracking

There are no ads and no ad networks in this app. No cross-app or cross-site tracking, no data brokers, and nothing sold or shared for anyone else’s marketing. You will never see an App Tracking Transparency prompt, because there is nothing to track.

Your control

Analytics is on by default and off in two taps: Settings → Data and privacy. Turning it off stops collection immediately and discards the anonymous id, so past events stop belonging to you. “Erase all data” in Settings clears the local database and the anonymous id together.

6. Purchases

Subscriptions and the lifetime purchase are sold by Apple through the App Store. Apple takes the payment. We never see or receive your card number, your billing address, or your Apple Account credentials.

We use RevenueCat to check with Apple whether a purchase is valid and to unlock Pro. RevenueCat receives an anonymous app user id and Apple’s receipt and transaction data — not your name and not your payment details.

You can manage or cancel a subscription in iOS Settings → your name → Subscriptions. Refunds are handled by Apple, not by us.

7. Notifications

Reminders are local. The app schedules them on your device. There is no push server, and no notification content is sent anywhere.

8. The Home Screen widget

The widget reads the same on-device storage through a container it shares with the app. Nothing is transmitted.

9. Third parties, in full

This is the complete list. There are no others.

• PostHog

  Anonymous product analytics

  Receives the anonymous usage and purchase events described in section 5. Processed on PostHog’s US cloud.

  PostHog privacy policy

• RevenueCat

  Purchase validation

  Checks with Apple whether a purchase is valid and unlocks Pro. Receives an anonymous app user id and Apple’s receipt data.

  RevenueCat privacy policy

• Apple

  Payments, App Store, HealthKit

  Takes the payment and runs the App Store. HealthKit is on-device only — nothing from it reaches us.

  Apple privacy policy

10. Retention and deletion

The data on your device lives until you erase it in the app or delete the app. We hold no copy of it.

Anonymous analytics events are kept by PostHog under our project’s retention setting. Because they carry no identifier we can tie back to you, the practical way to stop and shed them is the in-app opt-out plus “Erase all data”. If you would like us to raise a deletion request anyway, email bmi@resonance-logic.com.

11. Children

This app is not directed to children under 13, and we do not knowingly collect personal information from children.

12. Your rights (GDPR, UK GDPR, CCPA/CPRA)

You have the right to access, correct, delete and export your data, and to object to how it is used.

There is an honest asymmetry worth stating plainly: for the data on your device you exercise all of those rights yourself, on your device, instantly, because we hold no copy to hand over. For the anonymous analytics, our legal basis is our legitimate interest in improving the app, and the opt-out in Settings is unconditional — you do not have to give a reason and nothing in the app stops working.

We do not sell or share personal information as those terms are defined under the CCPA and CPRA. We do not use your data for cross-context behavioral advertising. This policy and any dispute about it are governed by the laws of the State of New York.

13. International transfers

Anonymous analytics events are processed on PostHog’s US cloud. If you are outside the United States, that means those events are processed there.

14. Changes to this policy

If we change this policy we will update the “Last updated” date at the top of this page and publish the new version here. If a change materially affects what we collect, we will say so in the app as well.

15. Contact

Resonance Logic, LLC — questions about this policy or about your data:

bmi@resonance-logic.com