NoctaliX
Join the waitlist
Your chest strap already knows how you slept.
NoctaliX records your heart overnight with the strap you train with, then turns it into HRV, sleep stages and a morning readiness score, synced to Intervals.icu.
The most precise sleep sensor is probably in your kit bag.
Rings and wristbands estimate each heartbeat by shining light through your skin. A chest strap reads the heart's electrical signal directly, so the time between beats, the raw material of HRV, comes out far cleaner.
You already trust that strap for your intervals. NoctaliX puts it to work for the other eight hours.
| Feature | Smart ring | Wristband | NoctaliX and your strap |
|---|---|---|---|
| How it reads your heart | Light through a finger | Light through the wrist | Electrical signal at the chest |
| Hardware to buy | A new ring | A new band | Nothing, if you own a strap |
| Subscription to see your data | Often | Usually | No, core features are free |
| Comfort | Barely noticeable | Barely noticeable | Takes two or three nights to get used to |
What you wake up to
A readiness score
One number that compares last night with your own baseline, so you know whether today is for intervals or for an easy spin.
HRV and resting heart rate
rMSSD, SDNN, lowest and average heart rate across the night, cleaned of artifacts and written straight into your Intervals.icu wellness.
Sleep stages
Deep, light, REM and time awake, estimated from how your heart behaves. With a Polar H10 we also use its motion sensor to spot restless moments.
A coach that reads your night
Plans your swim, bike and run sessions in Intervals.icu and on your Garmin, and adjusts them when your body says you're not recovered.
NoctaliX Age
How old your heart behaves, based on your overnight data and fitness, and how it moves as your training does.
How it works
Connect Intervals.icu
Sign in once. Your nightly results land in your wellness data, next to your training load.
Pair your strap
Any Bluetooth chest strap that sends heart rate and beat-to-beat intervals. You'll see your heart rate live before bed.
Sleep
Phone on charge by the bed, strap on. The recording runs in the background all night and reconnects on its own if the signal drops.
Help us test it first.
We're looking for Android beta testers who sleep with a chest strap and use Intervals.icu. Join the list and tick the beta box: we'll send you an invite when the closed test opens.
Questions
Isn't it uncomfortable to sleep with a chest strap?
For the first night or two you'll notice it. Most people stop noticing by the third night. Wear it a notch looser than when you train and wet the electrodes before bed.
Which straps work?
Most Bluetooth chest straps work, as long as they send beat-to-beat (RR) intervals along with heart rate: Polar H10 and H9, Wahoo TICKR, CooSpo and many more. Support varies by model, so before launch we'll publish the list of straps we've tested.
Do I need an Intervals.icu account?
Yes. NoctaliX writes your nightly HRV, resting heart rate and sleep into Intervals.icu, and the Premium coach plans your sessions there. Intervals.icu offers a free account.
Where does my data go?
Recordings are processed on your phone. Your nightly summary goes to your own Intervals.icu account. We don't sell data and there are no ads in the app.
Is NoctaliX a medical device?
No. NoctaliX is built for training and wellness. It doesn't diagnose or treat any condition. If you're worried about your sleep or your heart, talk to a doctor.
When can I use it? What about iPhone?
Android comes first, starting with a closed beta. iPhone follows. Tell us which phone you use when you join and we'll write when it's your turn.
Join the waitlist
One email when the beta opens, one when NoctaliX launches. Nothing else.