Privacy Policy
Last updated: November 8, 2026
Twin Tip Solutions ("we", "our", or "us") operates the Shoulder Rehab mobile application (the "App"). This policy explains what information the App handles and how.
1. The short version
- You don't create an account.
- Your measurement history, photos, and recovery details are saved on your device. We do not keep a copy of your photos or your history on our servers.
- If you turn on the AI photo check, each photo you measure is sent to our server to check its framing and is not stored there.
- We collect usage and crash data, tied to a random identifier rather than your name, to fix problems and improve the App. It includes a few recovery details, listed in Section 5. We never sell data or use it for advertising.
2. Information stored on your device
The following is saved on your phone. We do not keep a copy of it, except for the limited usage events described in Section 5:
- Recovery details: which shoulder you're tracking, your condition, and an optional surgery or injury date.
- Measurements: shoulder angles with their date, motion, side, and the points used to measure them.
- Photos: the photos you measure, so you can review them later.
Your device's own backup (such as iCloud or Google backup) may include this data according to your device settings. You can delete everything at any time in Settings > Delete all data, or by deleting the App.
3. Joint detection and AI photo check
Your hip, shoulder, and elbow are located on your device, without uploading anything. Separately, the App can have an AI model check that each photo is usable. Before the first check, the App asks for your consent. If you agree, then each time you measure, the App sends the following through a secure Google Cloud Function:
- the photo (resized, up to 1280 pixels),
- which motion you're measuring (flexion or abduction) and which side (left or right).
The photo is analyzed by Gemini, an AI model made by Google, running on Google Cloud Vertex AI, to check its framing and camera angle. The photo is used only for that request. We do not store it, and it is not used to train AI models. Google processes this data under its Cloud data processing terms and may hold it temporarily in memory while running the service. You can turn the AI photo check off at any time in Settings, in which case photos never leave your device.
4. Anonymous sign-in and usage limits
To protect the analysis service from abuse, the App signs in with an anonymous Firebase identifier. No name, email, or password is involved. Our server keeps a daily count of analyses per anonymous identifier to enforce a fair-use limit. These counters contain no photos or health details and are automatically deleted after a few days.
5. Usage and crash data
We use Google Analytics for Firebase and Firebase Crashlytics to understand how the App is used and to fix crashes (for example: app opens, whether an analysis or photo check succeeded, how long it took, crash reports, and device and operating system details). Usage events also include some recovery details: your condition category, which shoulder you are tracking, whether you set a recovery date, the motion measured, the measured angle, and whether you adjusted the points. This data is tied to a random app identifier, not to your name, and never includes your photos. As with any internet request, our services receive your IP address when the App connects to them. Google Analytics may use it to estimate your approximate location, such as your city or region.
6. Camera and photos
The App asks for camera access so you can photograph your arm, and lets you pick an existing photo from your library. These are used only for measuring your shoulder.
7. Notifications
If you allow notifications, the App schedules a weekly reminder on your device. Reminders are local and involve no server.
8. Third-party services
- Google Firebase (anonymous authentication, Cloud Functions, Firestore usage counters, Analytics, Crashlytics): firebase.google.com/support/privacy
- Google Cloud Vertex AI, running Google's Gemini model, for the photo check described in Section 3.
We do not sell, rent, or share your data with anyone else, and we do not use it for advertising or cross-app tracking.
9. Data deletion
Your history and photos live on your device, so deleting them in the App (Settings > Delete all data) or uninstalling the App removes them. This does not remove usage events already sent as described in Section 5. For any questions about data held by our services, email reid@twintipsolutions.com with the subject "Data Deletion Request."
10. Children
The App is not directed at children under 13, and we do not knowingly collect information from them.
11. Changes
We may update this policy. Changes will appear on this page with a new "Last updated" date.