Privacy Policy
Effective date: September 10, 2026
Overview
Kelvin ("Kelvin," "the App") is developed by Adelyons Software LLC ("we," "us," or "our"). Kelvin is a hardware-agnostic, local-first cold-exposure companion: a plunge timer (breath-up, a plunge countdown with a first-30s cold-shock safety coach, and a guided warm-up), a session log with history, streaks and a calendar heatmap, a breathwork trainer, and adaptation insights. It works with any cold source — ice bath, cold shower, lake, or tub. This policy explains how the App handles your information.
The short version: Kelvin is local-first. There is no account, no login, and no cloud backend. All of the information you enter — every session, temperature, duration, note, and streak — is stored only on your device and never leaves your phone. There are two narrow exceptions, neither of which involves your data: purchase and subscription data, which is handled by Apple, Google, and RevenueCat solely to validate an optional Kelvin+ purchase. The second is the optional invite feature (see Invite a Friend), which sends only a random installation identifier and an invite code. We never receive, sell, or have access to your data.
Not medical advice. Kelvin is a self-tracking and timing tool. It does not diagnose, treat, or prevent any condition and is not a substitute for professional medical advice. Cold exposure carries real risks — cold shock, afterdrop, and (with breath-holds in or near water) shallow-water blackout. Never do breath-holds in or near water. Consult a doctor before starting, especially with a heart condition, high blood pressure, or during pregnancy.
Information Stored On Your Device
The following is created and stored locally on your device only, in a private database (SQLite) within the App. It is not transmitted to us or to any server:
- Session logs: Date and time, water source (ice bath, shower, lake, tub, other), water temperature (°C), duration, and post-plunge clarity, plus any note you dictate through Siri voice logging (iOS).
- Streaks & stats: Current and longest streak, total time-in-cold, longest plunge, weekly minutes, and the calendar heatmap — all computed locally from your sessions.
- Protocols & breathwork: The four built-in protocols and your breathwork-trainer settings.
- Adaptation insights: With Kelvin+, your cold-capacity curve and the coach digest — both generated locally, by deterministic rule-based logic, from the data above.
- Health answers: Your answers to the optional health questions (heart condition or high blood pressure; pregnancy), used only by the on-device safety guardrails.
- App settings & preferences: Accessibility preferences (large text, high contrast, reduced motion), plus onboarding and review-prompt state.
Because this data lives only on your device, it is removed when you delete an entry in the App, clear the App's data, or uninstall the App.
No Account & No Cloud
- Kelvin does not require you to create an account, sign in, or provide an email address, name, or any other identifier.
- We do not operate a server that receives, stores, or backs up your data. There is no backend anywhere in the App.
- Your data is not synced between devices by us. If your device's operating system backs up app data (for example through iCloud or Android backup that you have enabled), that backup is controlled by you and your platform provider under their policies — not by us.
- You can create your own backup using the App's CSV export, which you save and share yourself.
Optional Purchases (Kelvin+)
Kelvin's core — the plunge timer, the cold-shock safety coach and guardrails, and the session log — is free forever, with an optional Kelvin+ upgrade. Purchases are the only feature that involves any data leaving your device, and they are handled by trusted providers:
- Apple App Store / Google Play: When you subscribe or make the lifetime purchase, the transaction is processed entirely by Apple or Google under their own privacy policies. We never receive or store your payment-card details.
- RevenueCat: We use RevenueCat to validate and restore your Kelvin+ entitlement. RevenueCat receives a purchase token, an anonymous app-generated user identifier, and basic device and purchase metadata needed to deliver and restore your purchase. It does not receive any of your session or health data — no sessions, temperatures, notes, streaks, insights, or protocols. See RevenueCat's privacy policy.
If you never make a purchase, no purchase-related data is sent. Subscription terms (including auto-renewal) are described in our Terms of Service, and are also governed by Apple's Media Services Terms and Google Play's Terms of Service.
On-Device Coach Digest (Not AI)
The optional Kelvin+ coach digest is produced by deterministic, rule-based logic that runs entirely on your device: it ranks findings from your own logs (volume, streaks, trends, your best week) and fills a fixed set of written templates, closing with a next-week ramp. There is no language model, no AI, and no model download, and it needs no network connection. Your session data is never sent anywhere to produce the digest.
Invite a Friend (Optional)
Kelvin includes an optional invite feature: if a friend enters your invite code, you both receive 30 days of Kelvin+ at no charge. It is entirely optional, and the rest of the App never needs a connection.
When — and only when — you open the invite screen or enter a code, the App sends the following to our invite service (hosted on Supabase) so the free month can be granted through RevenueCat:
- A random installation identifier generated on your device the first time the invite screen is used. It is a random value, not a device or advertising ID, and it is not derived from your device or from you.
- Your RevenueCat anonymous customer identifier, so the free month is applied to the right installation.
- The six-character invite code being created or redeemed.
That is the entire payload. It does not include your plunge sessions, timings, or history — none of your session data is involved in the invite feature in any way. We do not learn your name, email address, contacts, or location, and there is still no account and no login. Records of invite codes and redemptions are kept only to grant the reward, to prevent abuse, and as an audit trail; email us and we will delete yours.
What We Do NOT Collect
- We do not collect, upload, or store your session or health data on any server.
- We do not require an account, email address, name, or login.
- We do not collect location data. A "lake" or other water source is just a label you type — it is not GPS.
- We do not use advertising identifiers or any cross-app tracking, and we do not show ads.
- We do not use third-party analytics or crash-reporting SDKs in the App that send your usage or personal data to us.
- We do not sell or rent your personal information to anyone. There is nothing for us to sell — your data stays on your phone.
Data Retention & Deletion
Because your sessions, streaks, insights, settings, and notes are stored only on your device, you control them directly and they are kept for as long as you keep them:
- Delete in-app: Remove individual sessions at any time, or clear the App's data from within the App or your device settings.
- Uninstall: Deleting the App from your device permanently removes all of its locally stored data.
- Purchase records: Subscription and purchase records held by Apple, Google, or RevenueCat are retained under their respective policies. You can manage or cancel a subscription from your device's store settings.
Security
Your data stays within the App's private storage on your device, protected by your device's operating system. Communication with the App Store, Google Play, and RevenueCat for purchase handling, and with our invite service, uses encrypted (TLS) connections. No system can guarantee absolute security, but keeping your data on-device means there is no central database of your information to breach.
Children's Privacy
Kelvin is intended for adults practicing cold exposure responsibly. The App is not directed to children under 13 (or under 16 where applicable), and it does not request that children provide information to us. Because everything is local and we operate no server, we do not knowingly collect any personal information from anyone — there is nowhere for such data to be sent to us. If you believe a child has somehow provided information that reached us (which our architecture is designed to prevent), contact us using the details below and we will help.
Your Rights
Privacy laws such as the GDPR (EU/EEA/UK) and CCPA/CPRA (California) give you rights to access, correct, delete, and port your personal data, and to opt out of its sale. Because Kelvin does not collect or store your personal data on our servers, we hold nothing about you to disclose, correct, or sell. You can exercise full control over your in-app data using the deletion and export options above. For any purchase data held by Apple, Google, or RevenueCat, contact those providers or reach us using the details below and we will help.
Changes to This Policy
We may update this policy as the App evolves. Material changes will be reflected by updating the "Effective date" above and, where appropriate, through an in-app notice. Continued use of the App after changes take effect constitutes acceptance of the updated policy.
Contact Us
Questions about this policy or your data? Email dev@adelyons.com.
Adelyons Software LLC
https://adelyons.com