The circadian health coach · iOS · private beta
Align your biology
Align your day with your biology. Sunlight, sleep, fasting and grounding — connected by your circadian rhythm.
An invite when the beta opens.
Your day has a shape
Light, sleep, meals and rest follow the same 24-hour clock. biokei reads your day against that clock and suggests the next thing that brings you back into rhythm.
Sunlight
Know your dose of sun
Time in Daylight comes from Apple Health. On top of it, biokei models your UV dose and vitamin D and shows both on a dual dosimeter: burn risk on one side, vitamin D benefit on the other.
UV dose and vitamin D are estimates from a model — the app labels them that way.
Sleep
Sleep anchors the whole day
Duration, stages, resting heart rate and HRV — synced automatically from Apple Health, nothing to log. Sleep is the anchor the rest of your rhythm is read against: when you wake sets when to seek light, when to eat, when to wind down.
Fasting
An eating window, kept gently
A simple eating-window timer with a Live Activity and a widget, so your window is visible without opening the app. What matters is that meals land at a consistent time of day — in rhythm with everything else.
Grounding
Grounding, honestly labelled
ExperimentalEvidence for grounding is limited and early. We include it because some people find it calming — simple session logging, so you can track how it feels for you.
Day to day
What it feels like day to day
A closer look at how biokei actually shows up while you live your day.
All domains
See your day before you live it
One strip lays sleep, sun, fasting and grounding over the same circadian line, so you can see where the day stands against sunrise and sunset — and what to do next — without opening a single domain.
Sleep
See exactly how you slept
Every stage tracked through the night — when you were deep, when you were dreaming, the one time you stirred — read at a glance the moment you wake, not buried in a chart you have to decode.
Last night's stages
Fasting
Always know when you can eat next
The countdown updates in real time, right on your lock screen — no mental math, no wondering if it's time yet. The moment your window opens, you already know.
Sun
Where the sun sits right now
The same sun angle and live UV index that feed your dose model, plotted against today's arc — not just a number, the actual shape of your day in the sun.
Sun 42° · strongest 13:24
6UV
San Francisco, United States
Sun
Vitamin D, building over the month
One estimate that moves with your sun sessions — not a single day's number, but where you're trending against the optimal range.
65 nmol/L · est.
BuildingThis month
2h 20m
Avg daily
28 min
All domains
Achieve goals
Each day closes with a simple score across your four domains. The bar fills as your day does — no streaks to protect, just a week you can see taking shape.
Grounding
Not every surface grounds the same
Wet sand and grass conduct better than dry pavement — the model scores what you're standing on, so a session on grass and one on a sundeck aren't logged as the same thing.
Water
99%
Sand
91%
Soil
83%
Bare earth
79%
Grass
75%
Other
60%
Coach
A nudge toward whatever's slipping
When a domain falls behind the rest, biokei says so directly and links straight to it — instead of leaving you to notice the gap yourself.
Get your feet down
Grounding is lagging behind your other domains this week. A few barefoot minutes today would help.
Open Grounding →
We label down, never up
Most health apps blur the line between what a sensor measured and what an algorithm guessed. biokei keeps the line visible — it's the point of the product.
Measured
Sleep duration and stages, resting heart rate, HRV and Time in Daylight — read from Apple Health, straight from your devices.
Modelled
UV dose and vitamin D come from a model of weather, location, skin type and clothing — clearly marked as an estimate, not a measurement.
Experimental
Grounding is early science, not settled fact — so we label it experimental instead of dressing it up. You'll always know exactly what you're looking at.
Pricing
Free to build the habit, premium to see the pattern
Everything you need day to day is free, for good. Premium is for the moment you want to see how your domains connect and track your trends over time.
- ✓ Today's circadian home — sleep, sun, fasting and grounding in one view
- ✓ Fasting timer with Live Activity & widget
- ✓ Sun dosimeter with burn-risk alerts, always free
- ✓ Grounding log and today's sleep, automatically from Apple Health
- ✓ Cross-domain correlations — how sleep, light, meals and grounding move together
- ✓ History and trends beyond 30 days, with weekly and monthly reports
- ✓ Vitamin D projections, advanced widgets and data export
- ✓ Phase 2: direct Oura & Whoop score integrations
Annual
$39.99
~$3.33/mo
See monthly & lifetime pricing
Monthly
$6.99
per month
Lifetime
$89.99
pay once
Includes a 14-day free trial on every plan.
Safety is never behind a paywall — burn-risk warnings stay free no matter your plan. Join the waitlist and beta testers skip the trial above entirely: a full year of premium, free.
Get early accessGet early access
biokei is in private beta. Leave your email and you'll get an invite when it opens — that's all we'll send.
Why "biokei"
Kei (系) is Japanese for "system" or "lineage". biokei is your biological system — the one rhythm your sleep, light, meals and rest all belong to.
Made by Biokei Labs.