Apple Watch · iPhone · AI-powered
Your journal, captured
in fifteen seconds
Cairn turns fleeting thoughts into lasting clarity — record from your wrist, enriched with your biometrics and calendar, understood by AI.
From thought to insight
in moments
Speak from your wrist
Raise your watch, tap record. Cairn captures your thought in under 15 seconds — no phone needed. Your voice is transcribed on-device instantly.
Context is added automatically
Your heart rate, HRV, blood oxygen, and calendar load are silently attached to every entry — giving future-you the full picture of how you felt.
AI surfaces what matters
On-device AI finds patterns across your entries — the correlation between your meeting load and your best creative work, entirely private, entirely yours.
Built for the way
founders actually think
Apple Watch voice capture
The lowest-friction journal in existence. Raise your wrist, tap once, speak. Audio is transcribed on-device and synced to your iPhone automatically.
Core featureBiometric context
Every entry is stamped with your real-time HR, HRV, blood oxygen, and wrist temperature — giving your journal a physiological dimension no text alone can capture.
HealthKitCalendar intelligence
Cairn reads your calendar load — meeting density, back-to-backs, focus blocks — and correlates it with your energy levels and journal sentiment over time.
EventKitCompletely private by design
All AI processing runs on-device using Apple’s Foundation Models. Your journal and health data never leave your iPhone. Not even to us.
On-device AIWeekly AI summaries
Each week, Cairn synthesises your entries, biometric trends, and calendar patterns into a clear, honest reflection — what you did, how you felt, what to carry forward.
Foundation ModelsHandwritten note ingestion
Snap a photo of your notebook page. VisionKit OCR extracts the text and adds it as a journal entry — bridging your analog and digital thinking.
VisionKit · ProYour data belongs to you
Cairn's AI runs entirely on-device using Apple's Foundation Models. Your health data, journal entries, and biometrics are never transmitted to our servers, never used for advertising, and never sold. Full stop.
Simple, honest
pricing
Start free. Stay free if you want. Upgrade when Cairn becomes part of how you think.
Explorer
Free for 7 days, then limited
- Apple Watch voice capture
- On-device AI (Foundation Models)
- Biometric context per entry
- Weekly AI summary
- Calendar intelligence
- After 7 days: 3 entries/week max
- No AI insights after trial
Core
per month · or $34.99/year
- Everything in Explorer, unlimited
- Full biometric trend analysis
- Handwritten note scanning
- Cloud AI via your own API key
- Calendar correlation reports
- iCloud sync across devices
Pro
per month · or $69.99/year
- Everything in Core
- Managed Mistral AI — no key needed
- Deep cross-month pattern analysis
- Mood × biometric correlations
- JournalingSuggestions integration
- Early access to new features
All plans include a 7-day free trial. No credit card required. Cancel anytime.
What founders
are saying
“I’ve tried every journaling app. Cairn is the first one that stuck — because I never have to pick up my phone to use it.”
“The biometric correlation is genuinely revealing. I had no idea my creative output was so tightly linked to my HRV.”
“On-device AI and no account required — finally a productivity app that doesn’t treat my data as the product.”
Begin your first
cairn today
Free for 7 days. No account. No credit card.
Download on the App StoreRequires iPhone with iOS 17+ and Apple Watch Series 4 or later