Case Study: Successful development of a BLE app for...

The Project

Short: A medical technology startup developed a wearable device for continuous vital sign monitoring.

A medical technology startup developed a wearable device for continuous vital sign monitoring. The device measures heart rate and oxygen saturation. It transmits data to a mobile app via Bluetooth Low Energy (BLE).

The device required Class IIa medical product certification under the Medical Device Regulation (MDR). This placed strict requirements on software documentation and validation.

The Four Key Challenges

Challenge 1: Reliable BLE Connection

BLE connections between wearable and smartphone are affected by interference, distance, and movement.

Maintaining a stable connection during continuous vital monitoring — without gaps or data loss — required careful protocol design and extensive testing across device combinations.

Challenge 2: Energy Efficiency

The device had to achieve at least one week of battery life. Continuous data transmission and minimal battery consumption are fundamentally in tension.

Target Wake Time (TWF) scheduling and adaptive transmission intervals were used to balance real-time monitoring with battery longevity. BLE transmission intervals, wake cycles, and data buffering were all carefully optimized.

Challenge 3: Data Security Under GDPR

Heart rate and oxygen saturation data are health data under GDPR Article 9 — the strictest protection category. End-to-end encryption was implemented between wearable and app. Data in transit and at rest is encrypted.

Access is authenticated before any health data is displayed.

Challenge 4: MDR Certification Requirements

Software for Class IIa medical devices must comply with IEC 62304. This standard requires documented development processes, risk management records, and validation evidence.

Documentation had to be built into development from day one — not assembled retroactively at the end of the project.

The Solution Approach

Phase 1: Proof of Concept

The project started with standard development boards rather than custom hardware. This validated the BLE communication architecture and data transmission reliability before any custom hardware was ordered.

Early failure at low cost is better than late failure at high cost.

Phase 2: Parallel Development With Regular Integration Testing

Firmware and mobile app development ran in parallel, with regular integration testing sessions. Issues at the hardware-software boundary were identified and resolved during development — not at the end of the project.

Phase 3: Security-First Architecture

Encryption and authentication were implemented from the first sprint. Security was not added later. This avoided the common problem of discovering that a chosen architecture makes secure implementation difficult.

Phase 4: Documentation as Part of Development

MDR-compliant documentation was written alongside the code. Risk management records, test protocols, and design history files were maintained throughout the project. This reduced the certification effort significantly compared to retroactive documentation.

Results

Short: The application achieved stable BLE connectivity with a reconnection time under 800 milliseconds after interruption.

The application achieved stable BLE connectivity with a reconnection time under 800 milliseconds after interruption. Battery life exceeded the seven-day target in field testing.

GDPR and MDR documentation was ready at the end of development — not as a separate project phase.

The startup received Class IIa certification on schedule.

What Other Companies Can Learn From This Project

• Define regulatory requirements before writing the first line of code
• Invest in a PoC phase — it prevents expensive architectural changes later
• Treat security and documentation as part of development, not follow-on work
• Plan for BLE variability across device manufacturers and OS versions during testing

> "BLE enables use cases that felt like science fiction five years ago — with minimal power draw." — Björn Groenewold, Managing Director, Groenewold IT Solutions