Kelvin Support

Kelvin is a hardware-agnostic, local-first cold-exposure companion — a plunge timer, a session log with real history, streaks and a calendar heatmap, a breathwork trainer, and adaptation insights. It works with any cold source — ice bath, cold shower, lake, or chest-freezer tub — with no hardware, no pairing, and no expensive tub. Kelvin owns the practice, not the tub. It is not medical advice and not a substitute for professional care.

No. Kelvin is deliberately hardware-agnostic — there's nothing to pair, no router, and no $5,000 tub. Pick a cold source (ice bath, cold shower, lake, stock-tank, or freezer), choose it in the app, and start the timer. Kelvin tracks the practice on whatever cold you have.

The plunge timer is one guided flow: breath-up rounds to prepare, a plunge countdown with a first-30s cold-shock breathing coach that paces your breath through the initial gasp reflex, and a guided warm-up afterward. The cold-shock coach and the rest of the safety guardrails are free, never paywalled.

Each session records the date and time, water source, temperature (°C or °F), duration, how you felt, and your post-plunge clarity and mood — in a tap or two. Over time you get streaks, total time-in-cold, your longest plunge, weekly minutes, and a calendar heatmap. A real timer, session log, and history that actually work.

The trainer guides box breathing and Wim-Hof-style rounds to prep for the cold. It includes a hard safety lock that never lets you do breath-holds in or before water — because breath-holds in or near water can cause shallow-water blackout and drowning. Do breathwork on dry land, well away from the water, every time.

Kelvin is local-first. All of your data — sessions, temperatures, durations, water sources, notes, streaks, protocols, and insights — is stored only in a private database on your phone. There is no account and no cloud backend, and your data never leaves your device. The only information that ever leaves your phone is purchase/subscription data needed to validate Kelvin+ (handled by Apple, Google, and RevenueCat). See our Privacy Policy for full details.

The Kelvin+ coach digest turns your own logs into a plain-language recap of your week plus a personalized next-week ramp — non-diagnostic and grounded in your data. It runs a small language model (Gemma 3 1B) entirely on your phone. To keep the install small, the model isn't bundled; it's downloaded only if you opt in the first time you use the feature (roughly 500 MB). After that it works offline, and your session data is never sent anywhere to produce the digest. On devices that can't run the model, the feature is simply hidden and the rest of the app is unaffected.

With Kelvin+, adaptation insights show your cold-capacity curve trending up, your temperature-by-duration tolerance trend, time-in-cold banked this month, your best time of day for clarity, and your mood correlation. They're computed entirely on your device from your own sessions.

You can export your sessions and create a local backup from within the app (CSV), then save or share the file yourself. Because everything lives on your device, keeping your own backup is the best way to move to a new phone or recover after a reset.

Because everything is stored on your device, you're in full control. You can delete individual sessions in the app, clear the app's data from within the app or your device settings, or uninstall the app to permanently remove all of its locally stored data. There is no server-side copy for us to delete.

Kelvin's core — the plunge timer, the cold-shock safety coach and guardrails, and the session log — is free forever, no card needed to explore. Kelvin+ adds adaptation insights, the on-device AI coach digest, custom protocols and a contrast/sauna builder, goals & challenges with shareable streak cards, and unlimited history with advanced stats. Plans are: Monthly — $3.99/month, Annual — $19.99/year (recommended), and a one-time Lifetime — $39.99. All three unlock the same features. Prices may vary by region and are shown in the app at purchase.

Subscriptions are billed through your App Store or Google Play account — we can't trap you. On iOS: open the Settings app → tap your name → Subscriptions → Kelvin. On Android: open Google Play → tap your profile → Payments & subscriptions → Subscriptions → Kelvin. Cancellation takes effect at the end of your current billing period. (The Lifetime purchase is one-time and never renews.)

Sign in with the same Apple ID or Google account you used to purchase, open Kelvin, and use the "Restore Purchases" option in settings. Your Kelvin+ entitlement will be restored. (Note: your sessions are stored locally, so to move your data to a new device, use the in-app export/backup.)

Yes. Because your data lives on your device, the plunge timer, session log, breathwork trainer, protocols, and insights all work without an internet connection — and the app opens instantly with no login. It even works at a frozen lake with no signal. A connection is only needed to make or restore a purchase, or for the one-time on-device AI model download if you opt in.

No. 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. If you think you or someone else is in danger or having an emergency, call your local emergency number immediately.