Building a subscription-free smart health ring: IoT hardware meets biometrics

Adola AI — Thu, 12 Mar 2026 04:23:43 +0000

The problem with smart rings today

If you've ever looked at a smart ring, you've noticed the pattern: pay $299 upfront, then $6-$12/month for a subscription to see your own data. Oura does it. WHOOP does it in a different way. The data is locked behind a paywall.

I've been building Adola (https://adola.app) — a smart health ring that tracks 6 sensors with no subscription, ever.

What the ring tracks

Heart rate (PPG-based, 24/7)
SpO2 blood oxygen
Skin temperature (medical-grade, not wrist-estimated)
HRV (heart rate variability)
Skin conductance (stress/arousal)
Accelerometer/gyroscope for sleep + movement

The hardware architecture

The ring uses a custom PCB designed with KiCad, with custom Zen DSL for the layout. BLE 5.0 for data transfer, ~7 day battery life target, titanium body.

The firmware stack is bare-metal C on an nRF52840. The companion app handles data sync + visualization.

Subscription-free model

The business model is simple: one-time hardware sale. All data stays on-device and local — we have zero incentive to lock it behind an API paywall. Export to CSV/JSON anytime.

Pre-orders open today

We're taking $5 pre-order deposits to gauge demand before committing to the first manufacturing run. If you're tired of paying monthly fees to read your own HRV data, check it out: https://adola.app/reserve

Happy to discuss the hardware design, sensor choices, or BLE firmware stack in the comments.

Building Adola Ring: A Health Wearable Without the Subscription Trap

Adola AI — Wed, 11 Mar 2026 06:42:17 +0000

Most health wearables follow the same playbook: sell hardware at cost, lock the data behind a monthly subscription. Oura charges $6/month. Whoop charges $30/month. Even Samsung and Apple gate advanced health metrics behind premium tiers.

We are building Adola Ring to break that pattern. One purchase, all your data, no recurring fees.

The Hardware

Adola Ring packs six sensors into a titanium form factor under 3 grams:

PPG (Photoplethysmography) -- Dual-wavelength green + infrared LEDs for continuous heart rate, HRV, and SpO2 tracking
Skin Temperature Thermistor -- 0.1C resolution NTC sensor for circadian rhythm and cycle tracking
3-Axis Accelerometer -- Low-power MEMS accelerometer for sleep staging, step counting, and gesture detection
Electrodermal Activity (EDA) -- Micro-current skin conductance electrodes for stress response measurement
Bioimpedance (BIA) -- Body composition estimation via multi-frequency impedance analysis
Ambient Light Sensor -- Adaptive LED intensity and environmental light exposure logging

The MCU is an ultra-low-power ARM Cortex-M33 running at 64 MHz with a dedicated sensor hub coprocessor that handles continuous sampling while the main core sleeps. Target battery life is 7 days with all sensors active.

Privacy by Design

Every health metric is processed on-device first. Raw sensor data never leaves the ring unless the user explicitly exports it. The companion app stores data locally in an encrypted SQLite database. There is no cloud account requirement, no telemetry, no data brokering.

The firmware will be open-source after launch. Users can audit the entire data pipeline from sensor ADC to rendered chart.

Why This Architecture Matters

The standard wearable architecture offloads all processing to a phone app that phones home to a cloud backend. This creates three problems:

Latency -- Real-time biofeedback requires on-device inference, not round-trip cloud calls
Privacy -- Health data is among the most sensitive personal information; centralized storage creates a single breach target
Vendor lock-in -- When the company sunsets the cloud service, the hardware becomes a paperweight

Adola Ring runs a lightweight inference engine on the Cortex-M33 for sleep staging and activity classification. The BLE stack streams processed metrics to the companion app, which does visualization and long-term storage locally.

The Stack

Firmware: Zephyr RTOS, written in C with sensor drivers for each of the six sensors
BLE Protocol: Custom GATT service with characteristic-per-metric design for efficient polling
Companion App: React Native with local SQLite storage, no backend dependency
Charging Dock: USB-C magnetic pogo-pin dock with alignment magnets

Current Status

The ring is in late-stage prototyping. We are running validation on sensor accuracy against medical-grade reference devices and tuning the power management state machine to hit the 7-day battery target.

Early access is open now at adola.app for a $5 refundable deposit (total retail price will be $79.99). Early backers lock in the lowest price and get first-batch shipping priority.

What We Are Looking For

If you work on embedded health sensors, low-power BLE firmware, or privacy-preserving health data systems, we would like to hear from you. Drop a comment or reach out through the site.

Adola Ring: Own your health data. No subscriptions. No cloud dependency.

Reserve yours at adola.app

Forem: Adola AI