A Cold Plunge Timer & Ice Bath Tracker for Any Cold Source
Kelvin is a hardware-agnostic cold-exposure companion — a gorgeous 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 $5,000 tub. Kelvin owns the practice, not the tub.
What it does:
- Plunge timer — breath-up rounds, a plunge countdown with a first-30s cold-shock breathing coach, and a guided warm-up
- Session log — temperature (C/F), duration, water source, how you felt, and post-plunge clarity and mood, in a tap or two
- Streaks & calendar heatmap — current and longest streak, total time-in-cold, longest plunge, and weekly minutes
- Breathwork trainer — box breathing and Wim-Hof-style rounds, with a hard safety lock near water
- Free safety guardrails — cold-shock and afterdrop guidance, a sensible exposure ramp, and contraindication warnings
- Works with any cold source — ice bath, shower, lake, or tub; no hardware required
- Local-first & private — offline, no account, your data never leaves the phone
Coming soon to the App Store and Google Play.
How It Works
⏱️ The Plunge Timer
One guided flow, every session: breath-up rounds, a plunge countdown with a first-30s cold-shock breathing coach to ride out the gasp reflex, and a guided warm-up afterward. A real timer that works on any cold source.
📒 Session Log & History
Log temperature (°C/°F), duration, water source, how you felt, and post-plunge clarity and mood — in a tap or two. The basics the category leader still misses: a session log and history that actually work.
🔥 Streaks & Heatmap
A calendar heatmap and streak tracking keep you honest: current and longest streak, total time-in-cold, your longest plunge, and weekly minutes banked. Watch the practice add up.
🌬️ Breathwork Trainer
Box breathing and Wim-Hof-style rounds to prep for the cold — with a hard safety lock that never lets you breath-hold in or before water. Train your breath, not your luck.
🛟 Free Safety Guardrails
Cold-shock and afterdrop guidance, a sensible exposure ramp, contraindication warnings, and a hard lock on breath-holds near water. Safety the whole category ignores — free, never paywalled.
🔒 Private & Offline
No account, no login, no cloud. Every session lives in a local database on your phone and opens instantly — even at a frozen lake with no signal. Your data never leaves the device.
A Look Inside
Made for Every Cold Source
🧊 New to the Cold
- Start safely with a beginner exposure ramp and the first-30s cold-shock coach
- Pick a source — ice bath, shower, lake, or tub — and just start
- Free safety guardrails on every session, never paywalled
🏃 Athletes & Recovery
- Run contrast (sauna → cold) and athletic-recovery protocols
- Track temperature-by-duration tolerance and time-in-cold banked
- See best time of day for clarity and your mood correlation
🌬️ Breathwork & Wim-Hof
- Box breathing and Wim-Hof-style rounds in a dedicated trainer
- A hard safety lock — never breath-hold in or before water
- Pair breathwork with the plunge timer for a complete practice
Kelvin+
Kelvin's core — the plunge timer, the cold-shock safety coach and guardrails, and the session log — is free forever, and no card is needed to explore. Kelvin+ adds insight and ambition, and runs 100% on-device: adaptation insights, an on-device AI coach digest, custom protocols and a contrast/sauna builder, goals & challenges with shareable streak cards, and unlimited history with advanced stats. Billing is store-managed — cancel anytime in the App Store or Google Play. No dark-pattern trials; we literally can't trap you.
Annual
Best value — works out to about $1.67/month, billed yearly.
Monthly
Flexible month-to-month access to Kelvin+.
Lifetime
A single one-time purchase — no subscription, yours to keep.
Prices may vary by region and are shown in the app at the time of purchase. All three options unlock the same Kelvin+ features. Manage or cancel a subscription anytime in your device's App Store or Google Play subscription settings. See our Terms for full subscription details.
Privacy First — Your Data Stays on the Phone
Kelvin is built local-first. Here's exactly how it works:
- No account, no cloud, no server. You don't sign up or log in. There is no backend that receives your data — nothing to leak and nothing to fail.
- Your data never leaves the device. Sessions, temperatures, durations, water sources, mood and clarity notes, streaks, and protocols are stored only in a local database (SQLite) on your phone.
- On-device AI. The optional Kelvin+ coach digest runs a small model entirely on the phone (an opt-in download). It only summarizes your own logs — your data never leaves the device.
- You share, not us. Shareable streak cards and CSV exports are generated on your device and shared only if and when you choose.
- One billing helper. The only data that ever leaves your phone is purchase/subscription data, handled by Apple, Google, and RevenueCat to validate Kelvin+. They never receive your session or health data.
For complete details, see our Privacy Policy and Terms of Service.