Health trackers are bulky, complex, and always dead. Not anymore.
The Eternal Band is a bracelet with real sensors that charges itself. No cables, no fuss.
Powered by the day.
Eternal Band uses outdoor and indoor light to provide a continuous, effortless picture of your health. It adds insight to your life without adding a task to your list.
Fashion forward
No more chunky "gadget wrist". Eternal Band comes in classic leather and metal watch bands that go with any outfit, whether a dinner party or a morning run.
Powered by presence
No more missed runs or nights of sleep, no more niggling feeling that you've forgotten to plug something in. By running entirely on light you move through each day, we removed the need for cables. You don't serve this device, it serves you.
Data sans obsession
We've built research-grade sensors into this consumer device, but you shouldn't need to obsess over graphs to be healthy. Our Analysis Engine simplifies your sleep, heart, and movement to keep it relevant, and of course full data is still available for the nerds.
Everything-proof by design
Eternal Band doesn't have charging ports, making it immune to dust, water, and daily wear.
Distraction-free
Other wearables seem designed to nag you — our tech does the opposite, quietly taking notes on your health to view later.
Everyday Moments
Built for Life
Backed by scientists and engineers from
We're experienced engineers and designers obsessed with making products that won't get in the way of living. Eternal Band is our debut product, with more coming soon.
Tech Specs
Biosignals
- Body temperature trends (NIST-traceable thermal sensor)
- Steps + activity 24/7 (accelerometer)
- Heart rate + HRV trends (dual LED + custom PPG amplifier)
- Light level + sun exposure (PV)
Battery
- 60 days battery life assuming no charging (living in cave)
- Eternal battery life with 3 minutes of sunlight/day
Size
- Weight: ~7g
- Dimensions: 11 x 33 x 7 mm
- Band width: 8 mm
Durability
- <2 g of non-recyclable components per device
- No exposed charging port to corrode
Built to last
- Polished steel case that wears naturally
- >20 year battery longevity (estimated)
- Fully encapsulated for water + dust resistance (IP68)
Connectivity
- Supported on iOS + Android
- Automated updates via the Eternal app
- Two weeks of data saved on-device
FAQ
When will Eternal Band ship?
Devices are currently being tested with beta users, and the first production batch is expected to be ready by fall 2026. If any unexpected supply chain events affect our timelines, we will inform you promptly.
What does Eternal Band track?
Eternal Band measures a core set of biomarkers with great accuracy. For now that includes step count / activity, body temperature, heart rate, HRV, and light exposure. However, your exact experience may vary a little as the hardware is finalized.
Is there a subscription?
No.
Does Eternal Band charge even if I’m mostly indoors?
Yes, bright offices and naturally-lit homes are enough to keep Eternal Band going, and it is designed to last for months even with no light. However, Eternal Band charges best outside — three minutes of sunlight per day will keep it going forever.
Is preorder pricing the final price?
The current preorder price is discounted to reward early users. Pricing will increase for future batches.
How can I refund my preorder?
Email info@eternal.xyz with your receipt and we'll process the refund ASAP
(minus payment processor fees).
What size wrists does Eternal Band fit?
Eternal Band uses standard 8mm watch bands and fits wrist sizes from 14cm to 20cm. Additional band sizes will be available at launch.
Is Eternal Band waterproof?
Yes! Eternal Band is IP68 rated, meaning it can handle rain, sweat, showers, and swimming. Since there's no charging port, there are no openings for water to enter.
How accurate is Eternal Band compared to medical devices?
Eternal Band uses research-grade sensors calibrated against medical equipment. While not FDA-approved for medical diagnosis, our accuracy matches or exceeds other consumer wearables in independent testing.
Can I wear Eternal Band while sleeping?
Absolutely. Eternal Band was designed for 24/7 wear. At only 7 grams, most users forget they're wearing it. Sleep tracking is one of Eternal Band's core features.
What happens if it's cloudy for weeks?
Eternal Band stores 60+ days of charge, so even extended cloudy periods won't affect it. Cloudy days still provide some charging, and indoor lighting helps too. The app will notify you if battery gets low.
Does Eternal Band work with Apple Health / Google Fit?
Yes, Eternal Band syncs with Apple Health, Google Fit, and other major health platforms. You can export your data anytime.
How long will Eternal Band last before I need to replace it?
We estimate 20+ years of battery longevity. The stainless steel case is built to last, and there are no ports or buttons to wear out. We're building Eternal Band to be a lifetime companion.
Is my health data private?
Your data is encrypted and stored locally on your phone. We never sell your data. You can delete everything at any time. See our privacy policy for full details.
Can I change the band?
Yes! Eternal Band uses standard 8mm quick-release watch bands. Swap between leather, metal, silicone, or any third-party band to match your style or activity.
Do I need to keep Bluetooth on all the time?
No. Eternal Band stores two weeks of data on-device, so you can sync whenever convenient. Most users sync daily when they check the app, but it's not required.
Will there be different colors?
The first batch ships in polished stainless steel. We're exploring matte black and gold finishes for future batches based on demand.
Who is Eternal?
We're a team of engineers and designers from MIT, CMU, Google, and other top institutions. We believe technology should work for you, not the other way around. Eternal Band is our first product.
What if I have more questions?
Email us at info@eternal.xyz — we read every message and typically respond within 24 hours.
