Sleep Tracker That Works Offline and Keeps Data Local (2026)

Most sleep trackers pair with an app or a vendor cloud. A few keep the night on the phone. Offline is not one setting. It is a stack: does tracking run without the network, does anything upload later, and can you export the file.

Disclosure: I am Dovy, founder of Komori Care. We are building a contactless bedside sleep monitor, coming 2027, wellness only.

Quick answer

• Phone-only and offline: onSleep says every sleep record stays on the device, with no account and no cloud upload, and it works completely offline. Export is CSV and JSON. Logging nights is free. Pro unlocks full history, analytics past seven days and unlimited export. OpenSleep is open source, on-device, no account. Sleepr analyses audio on the iPhone and says tracking works in airplane mode. The sleep summary you choose to sync uses the network.
• Hardware trackers usually pair with an app. OZI connects to its app over Bluetooth, $199 as listed on ozisleep.com in October 2026, no monthly fee.
• DIY radar with ESPHome and the Seeed MR60BHA2 stays on your network and reports breath rate, heart rate and distance locally. Komori Care (2027) is designed to work offline with an SD card, with some features unavailable, and cloud is optional.

If you want the Home Assistant version of that DIY path, see Home Assistant sleep tracking with mmWave. If the worry is who holds the file, see Oura privacy concerns and local alternatives. For sleep data when friends stay, local storage still needs a guest rule.

Phone apps that stay on the device

onSleep is a tap-to-start diary. The site says nothing leaves your phone, there is no account, and export is CSV or JSON. Full calendar history and longer trends sit behind Pro. Phone-only nights track when you slept. Stages need a watch that writes to Apple Health or Health Connect.

OpenSleep tracks stages on the phone. No sign-up. The coach model downloads once and then chats with no connection.

Sleepr is the honest middle. Analysis is on-device and works in airplane mode. Optional summary sync is still a network step. On-device is not the same as local-only.

We could not open SleepViz (Cloudflare block), so it is not in this list.

Hardware that still talks to an app

OZI sits under the sheet. Setup is Bluetooth to the OZI SmartSleep app. No camera, no mic, no subscription, as listed on the product page. The night still lives in an app you install.

Most bedside lamps and under-mattress pads work the same way: the sensor can run without you watching it, then the log shows up after a sync.

DIY radar on your network

Seeed's MR60BHA2 through ESPHome exposes presence, breath rate, heart rate, distance and a target count. That is local Home Assistant data, not a finished sleep report. Seeed's wiki says vitals mode targets one stationary person within about 1.5 m.

Komori Care (coming 2027)

Komori Care is designed to work offline with an SD card, though some features are unavailable without the cloud. Cloud is optional. The sensing is 60GHz radar, no camera is required, an optional camera records to an encrypted SD card, and a one-press button cuts sensing. Coming 2027, wellness only.

FAQ

Do sleep trackers need internet? Depends on the device. onSleep and OpenSleep say they work without an account or cloud. Sleepr says tracking runs in airplane mode and only the summary you choose to sync uses the network. OZI pairs over Bluetooth. Ask the vendor for each SKU.

Is on-device the same as local-only? No. Sleepr analyses audio on the phone and still offers optional summary sync. onSleep says nothing is uploaded. Those are different promises. Read both pages.

What do I give up offline? For apps, onSleep says full history and analytics need Pro. For Komori Care, some features are unavailable without the cloud. Keep that general until launch.

Can I export my data? onSleep says CSV and JSON. Quote that page if you need the format.

Is a no-camera tracker private by default? No. Where the file sits still matters. See sleep tracker privacy comparison.

Keep reading

• Home Assistant sleep tracking with mmWave
• Oura privacy concerns and alternatives
• Sleep tracker privacy comparison
• Sleep monitor without a camera
• Best sleep tracker without a subscription
• Sleep tracker without a phone in the room

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Komori Care is a contactless sleep monitor in development. Camera-free position tracking, coming 2027. Wellness only. Join the waitlist.