A tamagotchi
of yourself.
Fernlet is a small companion for everyday care. It reflects the food, sleep, movement, rest, and other things you choose to log — without turning your life into a grade.
No streaks. No ads. No tracking. No account. Your health information stays yours.
Slept a little better last night.
What Fernlet leaves out
Fernlet is made to support your care, not keep you performing for an app. Each of these was possible, and left out on purpose.
- Streaks
- Calorie targets
- Weight goals
- Leaderboards
- Ads and tracking
- Accounts and logins
Slept a little better last night.
no percentage, no grade — just how the day is going
Up to 100 words, one colour tag. Sealed on the device — the AI can read your reflection, never the raw entry.
Three rings. There is no fourth ring, because there is no calorie target.
The companion is your biggest supporter.
Fernlet notices how you've been doing lately — thriving, okay, tired, or sick — and meets you there. It doesn't keep a scoreboard, and it won't punish you for a rough week.
Your day moves with you
Fernlet uses a rolling 24-hour window instead of a calendar day, so care still counts when the clock changes.
How your day is going, at a glance
A segmented bar shows the shape of your day — no percentage, no perfect score to chase.
It notices more than it lectures
Fernlet might mention that you slept a little better. It won't lecture you about what you skipped.
More gentle on hard days
If you're sick or having a difficult time, Fernlet responds with more room and less pressure.
Friends begin in person.
There is no public profile, discovery feed, or stranger requests. If two people choose to connect while they're together, two phones hold still 15 cm apart for the better part of a second — that's the handshake — and everything after that passes directly between their phones.
Three phones in one room. Nothing is connected, nothing is advertising.
Stand next to each other
Both of you tap Join. The phones find each other over a local, encrypted peer-to-peer link — no internet, no lobby to browse.
Touch phones and hold
Precise ranging measures the real distance. A friend is only committed after 15 cm for about 0.8 seconds. Phones never brought that close never connect.
No accounts involved
You exchange display names, public keys, companion looks and a fuzzy vibe. Your private keys never leave your device.
It fades when you leave
A session only lives while you're together — send recipes, companion decorations, and hearts back and forth, and support a friend by sending one when you think they need it. There's nothing left on a server once you go.
Friends see a name, a companion, and a broad wellbeing state — thriving, okay, struggling. They don't see your health records, score, goals, journal, or cycle data, and sharing ends when the connection ends. Your friend list stays small on purpose: 8 people.
Your cycle data stays separate.
Cycle tracking is kept apart from Fernlet's everyday features. It's not shared with friends, used for the companion, or included in ordinary iCloud sync — and you can choose whether to make a separate encrypted backup. That separation lives in the source code itself: wiring cycle tracking into the AI or networking code by accident breaks the build immediately.
Your period might be starting soon.
predicted on your phone — the prediction never leaves it either
Cycle data never leaves the phone unless you deliberately turn this on — a separate, clearly-warned opt-in, not part of ordinary iCloud sync.
Never touches the AI
On-device models cannot import the sealed store. No summaries, no suggestions, no reflections built from your cycle.
Never written to Apple Health
Fernlet reads sleep, steps and workouts from Health. It writes back only workouts — never period, mood, journal, hydration or hygiene.
Never in ordinary sync
It is excluded from iCloud sync and from your data export, so a shared laptop or a file you send someone can't carry it out with everything else.
Never visible to friends
In-person friends see a fuzzy vibe and a companion. There is no field in the handshake that could carry cycle information.
The wall breaks the build
A pre-merge script fails the build the moment the AI or networking code imports the sealed store — a compiler check that runs before every merge.
Intimate-activity notes sit in the same sealed store, are gated to 16+, and are hidden and off until you go looking for them.
Privacy shouldn't depend on a promise.
Fernlet has no ads, no trackers, and no developer-run server holding your health information. The app works without an account. Your everyday information stays on your phone; if you choose iCloud sync, it goes to your own private iCloud database, not one Fernlet operates. Sensitive information — journal text, cycle data, and similar notes — is kept separately and encrypted.
Period data, journal text, sensitive memories and intimate notes live in a sealed, encrypted store the AI and networking code physically cannot import — a build script turns any cross-wall import into a hard compile error.
Nothing above this line is ours. Optional backup goes to your own iCloud, sealed categories encrypted first.
servers the developer operates. No backend means no copy of you to leak.
iCloud, not ours — and sealed categories are encrypted before they leave the phone.
AI. Journal text, memories, health, photos and cycle data are never sent to an AI service.
commitments: data logged under this policy can never be retroactively repurposed.
Questions people actually ask
Is it free?
Yes, permanently — no price, no subscription, no in-app purchases, no ads. There is no business model that needs your data, because there is no business model that touches your data. Fernlet is also open source under Apache 2.0: every line, including the cryptography, is published at github.com/bowman-mw/fernlet, so you don’t have to take any of this on trust.
Do I need an account?
No. There is no sign-up, no login, no email, no password. The app works the moment you open it.
What happens if I miss a day?
That day scores lower. That is all. There are no streaks to break, and every unlock you have earned is cumulative and can never be taken back.
Does it count calories?
Never. You get macro goals — protein, carbs, fat — and nothing else. No calorie ring, no weight target, no body-composition anything.
Can my friends see my numbers?
No. Friends exchange display names, companion appearances and a fuzzy vibe — thriving, okay, struggling. Your score, goals, cycle data and raw health data never leave your phone.
What if I lose my phone?
If you turned on iCloud sync, your core data restores from your own iCloud. Sealed categories — cycle data, journal text, sensitive memories, intimate logs, your own photos — work differently: their key is locked to this phone's Secure Enclave, so no device backup can bring them back on a new phone. The only way to recover them is the optional encrypted sealed backup, which uses a key stored in your iCloud Keychain. If you lose access to that Keychain everywhere, that data is gone for good — the app tells you this before you turn the backup on.
Which iPhones does it need?
iOS 26 or later; iPhone 15 Pro or newer for the full on-device AI features. The 15 cm friend handshake needs a phone with precise ranging — on other phones you confirm on screen instead.
The plan, roughly
Built by one person, in the open. Most of this list has turned into real features already — what's left keeps the same rule: nothing here changes the privacy commitments.
- Meal logging overhaul + barcode scanning against a real food database
- Cooking mode with Live Activities
- Disposable-camera photowall + friend-mesh photo sharing
- Creation Studio clothing sharing
- Widgets and lock-screen glances
- Sealed-backup recovery and trainer session exports
- Full localization — translated strings, not just scaffolding
- Multi-device sync without iCloud
- Group workouts and shared sessions
Look at the code yourself.
Fernlet's source code, privacy policy, and technical documentation are public, including the network-egress inventory. Point a proxy at the app and check that the list is the whole list.