Concept renderRing
Smart ring
Sleep, recovery and readiness from the finger, where the optical signal is strong at night. The hard parts are a battery in a thin band of metal and a fit that holds across sizes.
Products · Health wearables
People stop wearing a ring that dies in two days or a band whose heart rate turns to noise on a run.
We design and build smart rings, screenless bands and health watches for AI health, fitness and sleep companies. PPG, SpO2, skin temperature and motion sensing, a battery sized for real use, raw data for your algorithm team, and health data that goes only to your cloud.
Concept renderForm factors
Where your sensors can live
The body location decides signal quality, battery size and how long people keep wearing it. Pick it with your algorithm team, not after.
Concept render
Concept renderBand
Screenless band
A sensor pod on a soft strap, worn day and night. No display means more room for battery and a lower price. Everything the user sees lives in your app.
Concept renderWatch
Health watch
A display for live heart rate, workouts and nudges without opening the phone. More power budget for the screen, and a larger enclosure to place the optical stack.
Clip
Clip-on or patch-style pod
A small sensor pod that clips to a waistband or sits in a reusable holder. Useful when the signal you need is motion or posture, not the wrist.
Strap
Chest strap
Heart-rate strap for training products that need a cleaner signal during hard exercise than the wrist can give.
Headband
Sleep headband
Soft fabric band for sleep and relaxation products. Comfort on a pillow drives the mechanical design as much as the electronics.
System
From the photodiode to your sleep score
A health wearable is five systems that must agree on timestamps, sample rates and what happens when data goes missing. We build the first four and test against the fifth.
- 01
Sensing
PPG LEDs and photodiodes, an IMU and a skin temperature sensor, placed and sealed in the real housing so the signal holds up on a moving wrist or finger.
- 02
Device
Sampling schedules, on-device buffering, optional on-device features such as heart rate or step count, encryption and signed OTA.
- 03
Sync
Bluetooth LE to the phone in batches, with resume on reconnect and no gaps in the night when the phone is out of range.
- 04
App & backend
Optional. Pairing, sync, device settings and a data API, deployed in your own cloud account.
- 05 · YOURS
Your algorithms
Your sleep staging, HRV, recovery and readiness models. We deliver the raw and processed data in the format your team expects.
Engineering record
Rings and watches our team has built
Our Shenzhen team has developed PCBA and firmware for smart rings and smart watches: Bluetooth LE, low-power design on Ambiq Apollo and Nordic SoCs, and wearable-size boards. Client names withheld.
Project specs, layouts and test data are shared on a call after a mutual NDA, where the client permits.
- Ring-size boards. Curved and rigid-flex layouts that fit inside a ring band, with sensor windows on the inner surface.
- Watch PCBA. Display, touch, PPG and IMU on one board, with the antenna kept clear of the metal case.
- Low-power firmware. Sensor duty cycling and sleep states on Ambiq Apollo and Nordic SoCs, measured per mode.
- Sync to the phone. BLE binding, buffered sensor data, resume after interruption and signed OTA updates.
Reference architecture
Inside a typical health wearable
Rings, bands and watches share the same blocks. The choices inside each block decide signal quality, runtime and size.
| Block | For example | Why it matters |
|---|---|---|
| SoC | Nordic nRF54L or nRF5340 series; Ambiq Apollo series where runtime matters most | Most of the power budget is spent here. Sleep current and sampling schedules decide whether you get days or a week. |
| Optical front end | Analog Devices MAX86141 or ADPD4100 class AFE, with green, red and infrared LEDs and one or more photodiodes | Green light for heart rate and HRV; red and infrared for SpO2 estimates. LED-to-photodiode spacing and light blocking matter as much as the chip. |
| Motion | Bosch BMI270 or ST LSM6DSO class IMU | Activity and sleep detection, and the motion reference used to clean up the optical signal. |
| Temperature | Digital skin temperature sensor, for example TI TMP117 class | Night-to-night trends depend on thermal contact with the skin and on keeping the sensor away from the charger and SoC heat. |
| Power | Small Li-ion cell (curved for rings), a PMIC such as Nordic nPM1300 or TI BQ25120A, fuel gauge | Charging contacts or a magnetic dock for open designs; wireless charging when the housing must stay sealed. |
| App & cloud | Your app and backend, or an app and backend we build in your cloud account | By default we deliver the device protocol and SDK and test against your endpoint; app and backend are an option. |
Part names are examples only. Final selection happens at Gate 0 against your sensing, runtime, size and cost requirements.
Key technologies
The engineering that decides whether your data is any good
Your models are only as good as the signal. Most health wearables fail on the optical stack, the fit or the battery. We work on all three from the first prototype.
- Optical stack and motion artifacts. LED and photodiode placement, light barriers, window material and skin contact pressure, tested on moving wrists and fingers. The IMU runs alongside so your algorithms can reject or correct motion.
- Ring sizing and fit. A size range that keeps the sensor against the skin, a sizing kit plan, and one electronics design that fits every size in the range.
- Battery and runtime. Runtime is a design target set at Gate 0 and measured on hardware, not a promise. Duty-cycled sensors, batched radio sync and a measured current profile per mode.
- Raw-data export. A raw-data mode with shared timestamps across PPG, IMU and temperature, documented formats and export tools for your algorithm team.
- Signed OTA updates. Firmware updates over Bluetooth LE with rollback, so you can ship sensor and algorithm changes after launch.
- Encryption. Data encrypted on the device and in transit, LE Secure Connections pairing, per-device keys provisioned on the line.
- Skin-safe housings. Materials chosen for all-day and all-night skin contact, sealed against sweat and water at the rating you need.
Regulatory path
What a health wearable must pass before you sell it in the US
A Bluetooth-only wellness wearable has a light radio path. The harder questions are your health claims and your users' health data. We map both at Gate 0 and file radio certifications in your company's name.
| Requirement | When it applies | What it means for you |
|---|---|---|
| FCC Part 15 Subpart C (§15.247) | Bluetooth LE transmitter | A ring often has no room for a pre-certified module, so plan for intentional-radiator testing on the final design. Bands and watches sometimes can use a module. |
| FCC Part 15 Subpart B | Every device with digital circuitry | Unintentional emissions. Still required when the radio module is pre-certified. |
| RF exposure (47 CFR §1.1307, §2.1093) | Worn against the body | Low-power Bluetooth LE often qualifies for an exemption. The lab confirms which applies to your design. |
| UN38.3 + 49 CFR §173.185 | Any lithium cell shipped with or in the device | Shippers and Amazon ask for the test summary. Plan it with the cell supplier at Gate 2. |
| IEC 62133-2 | Rechargeable cell and pack safety | Not a federal requirement, but many retailers ask for it. A cell that sits against skin all night deserves the test anyway. |
| FDA general wellness policy | Every health-related claim on the box, the app and your ads | FDA reissued its general wellness guidance on January 6, 2026. It allows non-invasive wellness products to estimate values such as heart rate variability or oxygen saturation, within limits. See the next section. |
| FTC Health Breach Notification Rule (16 CFR Part 318) | Health apps and connected devices not covered by HIPAA | A breach includes sharing health data without the user’s authorization, as well as a hack. Users must be notified within 60 calendar days of discovery. |
| Washington My Health My Data Act (RCW 19.373) | Consumer health data from Washington consumers | Covers data on bodily functions, vital signs and measurements. Collection needs consent for a specified purpose; sharing needs a separate consent. Enforced under the state Consumer Protection Act. |
| Illinois BIPA (740 ILCS 14) | Only if the product uses a biometric identifier | The Act lists retina or iris scans, fingerprints, voiceprints and scans of hand or face geometry. Relevant if you add fingerprint unlock or voice ID, for example. |
Rules as of October 2026. This is a planning summary, not legal advice. Primary sources: 47 CFR Part 15, 47 CFR §2.1093, 49 CFR §173.185, FDA general wellness guidance, FTC Health Breach Notification Rule, RCW 19.373, 740 ILCS 14. Lab and certification fees are paid by you; we manage the process. How we plan FCC work.
General wellness or medical device: the words decide
FDA's guidance looks at your labeling, advertising, user interface and functionality, not only the hardware. The same ring can be a wellness product or a medical device depending on what you say it does. Summary of the January 6, 2026 guidance, which superseded the 2019 version:
| Category | Examples from the guidance |
|---|---|
| Usually inside general wellness | Sleep tracking and sleep trends; physical fitness and activity; stress, relaxation and recovery; heart rate during exercise; values, ranges, trends and baselines shown in a wellness context. |
| Moves the product toward device regulation | Naming a specific disease, clinical condition or diagnostic threshold; alerts that recommend clinical action; treatment guidance; claims of clinical accuracy, "medical grade" or equivalence to a cleared device; an intended use of screening, diagnosis or monitoring of a disease. |
| Allowed with care | A notice that a healthcare professional may be helpful when readings fall outside wellness ranges, if it names no disease, does not call the reading abnormal, and gives no clinical thresholds. |
| Needs validation | Values that look like clinical values, such as SpO2 or blood pressure, should be validated, for example by manufacturer testing or peer-reviewed literature. |
Your regulatory counsel confirms your intended-use claims. We keep the firmware, the app copy and the validation data consistent with what counsel approves, and we can keep the hardware compatible with a later medical filing if you plan one.
Small batches
How a 10–1,000 units run works for a health wearable
Health wearables need data from real bodies before the design is frozen. The gates are built so your algorithm team gets that data early.
- Gate 1, works-like (3–5 units, 3–6 weeks). Sensor and SoC boards in a rough housing with a raw-data mode. Your team collects first recordings and checks the signal against a reference.
- Gate 2, EVT (10–30 units, 6–10 weeks). First custom PCB and enclosure, and for rings, the first size set. We measure runtime, signal quality in the housing and charging behavior.
- Gate 3, pilot (10–1,000 units, 8–16 weeks). A beta group wears the devices day and night. Certification and any validation testing run in parallel.
Every unit off the line goes through a production test we write with you:
- Optical calibration: LED drive and photodiode response measured against a reference target in a dark fixture, with limits set from EVT data
- IMU self-test and temperature sensor offset check against a reference
- Charge test through the real contacts or wireless pad, and current draw in sleep and active modes; battery capacity sampled per lot
- BLE conducted power check, unique key injection, and serial and public key logged to a file you keep
Data sovereignty
Health data goes to your cloud and nowhere else
Heart rate, sleep and temperature data is health data under laws like Washington's My Health My Data Act. The device is designed so that only you can read it.
- No Duobay server and no China-hosted service in the data path. Devices talk to your app and to a US cloud region you choose.
- You generate and hold the signing keys and device credentials. We can run key injection with keys your team provides.
- Sensor data is encrypted on the device and in transit, and deleted from the device after a confirmed sync.
- You receive the firmware source and a software bill of materials (SBOM) listing every library, version and license.
- We document data flows and security design so your counsel can map consent, sharing and breach-notification duties.
Health wearables: common questions
Can our ring show SpO2 or HRV without FDA clearance?
Possibly. FDA’s general wellness guidance, reissued on January 6, 2026, says non-invasive products that estimate values such as oxygen saturation or heart rate variability may be general wellness products when the outputs are for wellness use only and clinical-looking values are validated. Your regulatory counsel confirms based on your intended-use claims. We keep the claims, the app copy and the validation data consistent.
How long will a ring run on one charge?
It depends on battery size, sampling rates and how often the radio syncs. A week between charges is a common design target for rings, not a promise. We measure real current draw per mode on the Gate 1 prototype and show you the trade-offs before the enclosure size is fixed.
Can our algorithm team get the raw sensor data?
Yes. We build a raw-data mode that streams or logs PPG channels, accelerometer and temperature with shared timestamps and documented sample rates, plus export tools. Your team trains and tests on data from the actual housing, not a dev kit.
Do our models run on the device or in the cloud?
Either. Simple features such as heart rate or step count often run on the device to save radio power. Sleep staging and recovery scores usually run in your app or your cloud. We can port a model to the device if it fits the memory and power budget, and we leave the model itself with you.
Can you build the companion app and backend?
Yes, as an option. We build the iOS and Android app for pairing, sync and settings, and a data backend deployed in your own cloud account. Your algorithms stay with you. App, cloud and AI.
Has your team built rings and watches before?
Yes. Our Shenzhen team has developed PCBA and firmware for smart rings and smart watches on Bluetooth LE, including Ambiq Apollo and Nordic platforms. Client names are withheld.
Next step. Tell us about your form factor, the signals your algorithms need and your target pilot size. A Duobay engineer replies within 2 business days.