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, the protocol's plunge duration, the cold source, water temperature (°C), and your post-plunge clarity — 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 to prep for the cold, and Wim-Hof-style rounds run through the timer's Wim-Hof-style protocol. The box-breathing trainer won't start until you confirm you're on dry land, and the timer warns you never to hold your breath in or near 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, cold sources, clarity ratings, health answers, 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) and, if you use Invite a friend, an invite code with an anonymous install id. See our Privacy Policy for full details.

The Kelvin+ coach digest turns your own logs into a plain-language recap (volume, your longest plunge, streaks, and trends once there is enough data) and closes on a sensible next-week step. It is a rule-based template engine, not AI: there is no language model and nothing to download, it works offline, and your session data is never sent anywhere. The digest text is currently in English in every language.

With Kelvin+, adaptation insights show your cold-capacity curve (one bar per week, combining temperature and duration) and the coach digest. They're computed entirely on your device from your own sessions.

Settings → Export CSV exports every session through the share sheet so you can save the file yourself. Kelvin has no backup or restore, so the export is a record of your sessions rather than a way to load them into Kelvin on another phone.

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 cold-capacity curve and the coach digest. 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 and do not move with your purchase.)

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.

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.