HealthOS
Personal · local-first · open-source

Your health.
In one app.
On your device.

AI-generated workout plans, photo food logging, and a daily coach that reads the last seven days of you. Local-first, bring-your-own key, no subscription.

View on GitHub → See how it works
iOS · Android React Native · Expo MIT licensed
Four pillars, one app

Everything for body recomposition.

Most fitness apps make you stitch together a food tracker, a workout planner, a body-fat calculator, and a coach. HealthOS is the four of them, in one calm interface, talking to each other.

01

Nutrition

Snap a meal, get calories and macros from Gemini vision. Or scan a barcode. Or type it in. Daily totals against personalised targets.

02

Training

AI generates a periodised plan from your split, equipment, and experience. Session logger tracks sets, reps, and progressive overload.

03

Body

Body fat (Navy, FFMI), BMI, BMR, TDEE. Weight trend, tape measurements, progress photos — all framed as trends, not pass/fail.

04

Coach

A short, daily, recomp-aware insight from Gemini that synthesises everything you logged. No motivational shouting. Just one helpful sentence.

AI workout plans

A new plan, built for you, in fifteen seconds.

Tell HealthOS your training split, equipment, days per week, and experience level. Gemini returns a periodised PPL, Upper/Lower, or Full-Body programme — sets, reps, rest periods, and a rationale you can read and trust.

  • Periodised 4 to 12 weeks, with explicit progression rules
  • Built around the equipment you actually have
  • Compound lifts first, isolation last — coach-grade structure
  • Rationale you can read, so you understand the why
Generated PPL workout plan with day cards and exercise list
Photo food logging

Point. Snap. Logged.

No more typing "grilled chicken breast, 150g". Take a photo of your plate and Gemini's vision model identifies the ingredients, estimates portions, and writes the macros into your daily log. Wrong on something? Tap to fix it.

  • Calories and full macro breakdown from a single photo
  • Barcode fallback via Open Food Facts when you want exact
  • Manual entry always available, with portion calculator
  • Confidence indicator on every AI estimate
Food log screen showing scanner card, daily totals, and meal sections
Daily coach

One sentence. Read in seven days of you.

Every morning the coach reads the last seven days of food, training, and body data and writes you one short, recomp-aware insight. No motivational platitudes. No "crush it today" energy. Just the one thing that's actually worth knowing right now.

  • Synthesises nutrition + training + body data, not just one signal
  • Knows surplus on training days, slight deficit on rest days
  • Weekly highlight pulls out the win or the watch-out
  • Tone bucket (win / nudge / watch / neutral) drives the visual frame
AI coach screen with Gemini-generated insight and weekly highlight
Local-first by design

Your data stays.

Everything lives in SQLite on your device. No accounts, no cloud sync, no analytics. The only outbound calls are the AI features you trigger — and even those use a key only you control.

No backend

There is no server. There is no database we host. There is no copy of your history anywhere except on your phone.

Bring your own key

You sign up for a free Gemini key once and paste it into onboarding. It's stored in the device secure enclave. We never see it.

Open source

Every line is on GitHub, MIT licensed. Read the prompts. Audit the network calls. Fork it and ship your own.

Honest about it

Built for one. Maybe useful for you.

Most landing pages bury the limitations. We give them equal billing — so you know what you're signing up for before you clone the repo.

What you get

Things HealthOS does well.

  • Privacy by architecture Your data never leaves the device. Not "we promise" — there's literally no server to leave to.
  • No subscription Bring a free Gemini key. Free tier covers ~1500 requests a day, comfortably enough for personal use.
  • Recomp-tuned defaults Macros default to high-protein. The coach knows surplus-on-training-days. Trends, not daily pass/fail.
  • AI features that work Photo food scanning, plan generation, daily coaching — all first-class, not bolted-on chat widgets.
  • Forkable Plain TypeScript, well-tested formulas, MIT licensed. Tweak the prompts. Ship your own version.

What you don't get

Trade-offs we made on purpose.

  • No cloud sync Switch phones and you lose history unless you export first. This is a deliberate trade-off, not an oversight.
  • BYO API key You have to create a free Gemini key once during onboarding. It takes a minute, but it's an extra step.
  • Free tier has limits Heavy users — lots of photo scans plus plan regenerations plus coaching — can hit Gemini's free quota.
  • Personal project Built for one user (me). No support contract, no SLA, no roadmap commitments. Bugs may take a while.
  • Not medical advice Formulas (BMR, TDEE, body fat estimates) are well-known approximations. Directional, not diagnostic.
Quick start

Three steps. No accounts. No backend.

Step 01

Clone & install

You need Node 20+, pnpm, and either Xcode or Android Studio.

git clone https://github.com/jkguidaven/healthos.git
cd healthos
pnpm install
Step 02

Run on your phone

One command, one simulator. Hot reload from there.

pnpm ios
# or
pnpm android
Step 03

Bring your key

Get a free Gemini key from Google AI Studio and paste it into the onboarding screen. It's stored in the device secure enclave.