Privacy Policy

§ 01Introduction

This Privacy Policy describes how SYLERO B.V. ("SYLERO", "we", "us", or "our") handles information in connection with the Workout Lens iOS application ("the App"), including the optional AI Coach Pro subscription features.

By using Workout Lens you acknowledge that you have read and understood this Privacy Policy. If you do not agree with it, please do not use the App.

§ 02Data controller

The data controller responsible for the App is:

SYLERO B.V.
Chamber of Commerce (KVK): 69820309
VAT: NL858025607B01
The Hague, the Netherlands
Email: hello@sylero.nl

For privacy-related inquiries you can also reach us at the same address with the subject line "Workout Lens — Privacy".

§ 03Data we access

Workout Lens requests read access to your Apple Health (HealthKit) data to provide its core functionality: generating workout exports and powering the on-device AI Coach features.

Workout metadata

• Workout type (running, cycling, swimming, strength, walking, …)
• Start time, end time and duration
• Source application and source device
• Workout effort score (where reported by your device)

Per-workout measurements

• Heart rate time-series
• Cadence (steps or revolutions per minute)
• Running speed, pace and distance
• Active energy (kilocalories)
• Elevation / altitude change (where available)
• Lap and split events
• GPS route points (latitude, longitude, altitude, timestamp)

Overnight and daily readiness signals (AI Coach Pro)

• Heart-rate variability (HRV, SDNN)
• Resting heart rate
• Lowest sleeping heart rate
• Body temperature (where available)
• Sleep duration, stages and timing (REM / Deep / Core / Awake)
• Respiratory rate
• Blood oxygen saturation (SpO₂)
• VO₂ Max estimate
• Heart-rate recovery (one minute after exercise)
• Daily step count, walking/running distance and exercise minutes

Body composition & health metrics

To power the trend charts on the in-app Health info page, the App also reads the following measurements where you have recorded them. All access is read-only; the App never writes to, edits or deletes data in Apple Health.

• Body weight
• Body Mass Index (BMI)
• Body fat percentage
• Height

Access is granted through the standard iOS HealthKit permission dialog. You can grant or revoke any of these permissions at any time via Settings → Privacy & Security → Health → Workout Lens on your iPhone.

The App does not access clinical health records, nutrition data, mental-health categories, reproductive-health data, or any other HealthKit category not listed above. It does not access your camera, microphone, contacts, photos library, or location outside the GPS data already recorded inside a HealthKit workout.

§ 04AI Coach Pro

AI Coach Pro is an optional subscription that adds a daily readiness score, an adaptive weekly training plan, per-workout AI analysis cards and an on-device chat with a local large-language model (LLM).

Where the AI runs

The language model used by AI Coach Pro runs entirely on your iPhone on the Apple Neural Engine. After purchase, the model file (approximately 2 GB) is downloaded over Wi-Fi from Apple's servers and cached locally. From that point on, generating a coach response does not require any network connection and no tokens, prompts or completions are transmitted to SYLERO or to any third party.

What the AI is told about you

When you ask a question, the App assembles a context window from data already on your device: your most recent workouts, your readiness signals, your training profile (sport, goal, preferred schedule), any context tags you have added (see below), and your previous chat messages in the same conversation. That context is given to the local model. None of it leaves your phone.

Your name

You can optionally set your name on the Profile page so the coach can address you personally. Your name is stored locally on your device and is passed only to the on-device AI coach as part of its context. It is never transmitted to SYLERO or any third party. The App does not access your Contacts to obtain it, and leaving the field blank is fully supported.

Context tags

On the day timeline you can add tags such as caffeine, alcohol, stress or illness to give the coach extra context. These tags are stored locally on your device and, like everything else, never leave it.

What we never collect

We do not maintain a server-side copy of your chat history. We do not collect prompts. We do not collect responses. We do not collect telemetry about which questions you ask or which features you use.

§ 05How we process data

All data processing takes place entirely on your device. The App reads HealthKit data, computes readiness scores and training-plan suggestions, formats workout exports into structured CSV files, and powers the AI Coach using the on-device language model. No personal data is transmitted to SYLERO's infrastructure at any point.

Export files are created locally in your device's temporary storage and handed to the iOS Share Sheet. What happens to a file after you share it — for example, if you send it to a cloud service, an AI chat product, or email — is governed by the privacy policy of that destination service, not by this policy.

The App does not include any analytics SDKs, advertising SDKs, crash-reporting SDKs, attribution libraries, or other third-party tracking. No usage data, telemetry or diagnostic information is collected.

§ 06Subscriptions

AI Coach Pro is available as an auto-renewable subscription that you purchase through Apple's App Store. We use Apple's StoreKit framework to verify your entitlement on-device.

Apple processes the actual payment, billing and refunds. We do not receive your credit-card number, your Apple ID, your name or your email address from Apple. We receive only an anonymous, cryptographically-signed receipt that tells the App whether your subscription is active. You can read Apple's privacy policy at apple.com/legal/privacy.

For aggregate reporting purposes Apple may share anonymised sales statistics with us through App Store Connect (e.g., number of subscriptions per country). These reports do not identify individual users.

§ 07Demo mode

The App offers an optional Demo mode that lets you explore every feature using pre-generated sample workouts instead of your real Apple Health data. Demo mode is fully local; no fake or real data is sent anywhere. You can switch in or out of demo mode at any time, and switching out instantly restores access to your real HealthKit data.

§ 08Legal basis (GDPR)

Workout Lens is designed for users in the European Economic Area (EEA) and complies with the General Data Protection Regulation (GDPR). Because all processing happens locally on your device and we receive no copy of your data, SYLERO does not act as a data processor or controller of your HealthKit data in the traditional sense. However, to the extent that any processing of health data falls within the scope of the GDPR:

• Art. 6(1)(b) GDPR. Processing is necessary to perform the service you requested — generating workout exports, readiness analysis, and AI coach responses.
• Art. 9(2)(a) GDPR. Health data is special-category data. Your explicit consent is obtained through the iOS HealthKit permission dialog before any health data is accessed.
• Art. 6(1)(b) GDPR — subscription contracts. For the AI Coach Pro subscription, processing of your purchase entitlement is necessary to perform the contract you entered into through the App Store.

§ 09Data sharing

SYLERO does not share, sell, rent or otherwise disclose your health data to any third party. We receive no copies of your data, so we have nothing to share.

The only "sharing" that occurs is when you use the iOS Share Sheet to export a workout file or copy a coach answer. This action is entirely under your control. The recipient (e.g. an AI application, a cloud storage service, an email recipient) is chosen solely by you.

§ 10Data retention

SYLERO retains no health data. All data remains on your device. The App caches certain derived state locally (your daily readiness snapshot, your training profile, your override choices) inside the app sandbox so it can render quickly. This local cache lives only on your iPhone.

Export files generated by the App are temporary and are not persisted by the App itself. If you save an export to your device (e.g. via the Files app), it is stored under your control, subject to your device's own storage and iCloud settings.

Deleting the App from your iPhone removes the App and all its local storage, including the on-device LLM model. It does not affect data inside Apple Health, which is managed by iOS and Apple.

§ 11Security

Because no data is transmitted to any external server, the attack surface of Workout Lens is significantly smaller than that of cloud-based applications. Your data is protected by the same iOS security mechanisms that protect all HealthKit data — including device encryption, sandboxing and the HealthKit access-control layer.

We recommend keeping your iPhone's iOS version up to date to benefit from the latest Apple security updates.

§ 12Third parties

The App uses the following first-party Apple services. None of them transmit your health data to us.

• Apple HealthKit. Read-only access to the health data described in section 3, governed by your HealthKit permissions.
• Apple StoreKit. Verifies your AI Coach Pro subscription on-device through a cryptographic receipt.
• App Store / iCloud. Distributes the App and the one-time language-model download.
• Apple Neural Engine. Runs the on-device LLM locally.
• Apple Notification service. Delivers local push notifications about new workouts. Local notifications are scheduled by the App and not routed through any server.

Workout Lens does not integrate any third-party analytics SDK, ad network, attribution SDK, marketing automation tool, A/B-testing framework or crash-reporting service.

§ 13International users

The App is offered worldwide. Because we do not collect personal data, there are no cross-border data transfers to SYLERO. Apple handles App Store distribution and may transfer transactional payment data internationally in accordance with its own privacy policy and Standard Contractual Clauses.

§ 14Your rights (GDPR)

As a data subject in the EEA, the UK or Switzerland, you have the following rights. Because Workout Lens is local-only, most rights can be exercised directly on your device.

Access (Art. 15)

All data the App accesses is visible in the App itself.

Rectification (Art. 16)

To correct health data, please do so in the Apple Health app on your iPhone.

Erasure (Art. 17)

You can revoke Workout Lens's access to your health data at any time via iPhone Settings. Deleting the App removes all local data, including the on-device language model.

Restriction (Art. 18)

Revoke HealthKit permissions at any time via Settings → Privacy & Security → Health → Workout Lens.

Portability (Art. 20)

Workout Lens is itself a data-portability tool — it exports your HealthKit data in machine-readable CSV format on demand.

Object (Art. 21)

You may object to processing at any time by revoking HealthKit permissions or deleting the App.

Complaint

If you believe your privacy rights have been infringed, you have the right to lodge a complaint with the Dutch supervisory authority:

Autoriteit Persoonsgegevens (AP)
autoriteitpersoonsgegevens.nl

§ 15Your rights (CCPA — California residents)

If you reside in California, you have rights under the California Consumer Privacy Act (CCPA) and the California Privacy Rights Act (CPRA), including the right to know what personal information is collected, the right to delete personal information, the right to opt out of sale or sharing, and the right to non-discrimination.

Because Workout Lens does not collect, sell or share personal information with anyone, in practice there is no information to disclose, delete, or stop sharing. We do not engage in any "sale" or "sharing" of personal information as those terms are defined under the CCPA/CPRA.

§ 16Children's privacy

Workout Lens is not directed at children under the age of 13 (or 16 in jurisdictions where that is the applicable age of digital consent). We do not knowingly collect any personal information from children. If you believe a child has used the App and you have concerns, please contact us at hello@sylero.nl.

§ 17Changes to this policy

We may update this Privacy Policy from time to time. When we do, we will revise the "Effective date" at the top of this page. For material changes, we will also update the App Store description and may show an in-app notice. Continued use of Workout Lens after changes constitutes acceptance of the revised policy.

§ 18Contact

If you have any questions, concerns or requests regarding this Privacy Policy or the handling of your data, please contact us: