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Native Mobile Apps for the World's First Wireless Breast Pump
Elvie needed native mobile apps to bring their wireless breast pump to market. Apps capable of controlling two pumps simultaneously via BLE, syncing multi-session data into a single model, and meeting FDA and MDR compliance requirements. Monterail has built iOS and Android applications from the ground up, helping Elvie grow into a FemTech market leader.
The company and product
Building the Software Behind the World's Best-Selling Wireless Breast Pump
Elvie is a British FemTech company founded in 2013, currently part of U.S. Willow Innovations, with a mission to improve women's lives through smarter technology. Their flagship products address the pelvic floor health and breastfeeding categories, including the award-winning Elvie Pump. The world's first wireless, wearable, silent, and smart breast pump.
The company operates in a highly regulated sector, where mobile companion apps for medical devices must comply with FDA Class II requirements and the EU Medical Device Regulation (MDR).
Before engaging Monterail, Elvie had the hardware concept for a wearable, wireless breast pump, but lacked the mobile software to bring it to life. The entire iOS and Android application layer needed to be built from scratch, in close coordination with the hardware team developing the pump itself.
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KEY CHALLENGES OF THE PROJECT
Controlling two Elvie Pump devices simultaneously
Via Bluetooth Low Energy (BLE), across different hardware generations (Pump, Pump+, Stride), each with different BLE API specifications, while delivering an identical user experience across all.
Synchronizing session data
From two separate pumps into a single, coherent session model. Milk volume, timing, and per-breast history had to merge correctly regardless of which combination of devices was in use.
Building for regulatory compliance from day one
FDA Class II exemption and MDR documentation requirements shaped architecture decisions at every layer, including data security and the design validation process.
Automating end-to-end regression testing for a physical hardware product
Manual testing across iOS and Android for each new pump generation was not sustainable. A hardware-in-the-loop testing approach was needed.
Optimizing hardware-software through strategic collaboration
Monterail advised Elvie’s hardware team on embedded software and chipset selection (Nordic semiconductors), which reduced development time, cut costs, and resulted in a highly stable product ecosystem.
OUR APPROACH
The Infrastructure That Kept Elvie's App Scalable for Eleven Years
Discovery and Architecture
We worked hand in hand with Elvie's internal hardware team. The first phase focused on mapping the BLE communication protocol across pump models and designing an abstraction layer to normalize device communication, so that the app logic remained consistent regardless of which pump generation was connected.
Cross-Device BLE Communication
The core technical decision was to build a unified BLE abstraction layer sitting between the hardware interface and the application logic. The abstraction layer translated device-specific BLE APIs into a single internal protocol, which allowed us to support Elvie Pump, Pump+, and Elvie Stride within the same codebase.
Data Synchronization
Session merging was handled through a custom synchronization service. It treated each pump as an independent data source and applied deterministic merge rules to combine per-breast volume, timing, and session history. The result was a single unified session model that the user saw in the app.
Automated Regression Testing
To make regression testing repeatable across hardware, Monterail built an automated test rig. We used real iOS and Android devices connected to an actual Elvie Pump. This setup allowed the QA team to run full end-to-end tests covering BLE connectivity, session recording, data sync, and UI flows, triggered automatically on each build.
Compliance and Validation
The design validation process was automated using a screenshot-generation system that produced documentation for every app module in all supported languages. It significantly reduced the manual effort required for FDA and MDR submission reviews and kept validation artifacts up to date with each release.
R&D and AI Prototyping
Beyond delivery, Monterail took an active role in proposing new product directions. The team designed and tested PoC features to explore how emerging technologies, including AI-based milk volume analysis algorithms, can extend the app's value. Structured validation allowed Elvie to make informed decisions about where to invest, with evidence rather than assumptions.
application functionalities
TECHNOLOGIES WE USED
| Layer | Technologies |
|---|---|
| Mobile | iOS (Swift) Android (Kotlin) React Native (cross-platform) |
| Backend / Cloud | AWS Node.js Data sync services |
| Hardware / BLE | Bluetooth Low Energy (BLE) BLE API abstraction layer Arduino (test rig) |
| QA & Testing | Automated E2E regression Real device test farm iOS & Android |
THE RESULTS
The Deliverables Behind an Award-Winning Medical Wearable
The measure of this project isn't just what was launched in 2019. It's what held up across three pump generations, seven years of releases, and every FDA review in between.
2 native apps (iOS + Android) built from scratch
BLE abstraction layer supporting 3 pump generations (Pump, Pump+, Stride) within a single codebase
Custom data sync service merging multi-pump session data into a single coherent model across all device combinations
Automated hardware-in-the-loop test rig (Arduino + real iOS/Android devices) replacing manual QA across hardware generations
Automated screenshot generation system covering all app modules in all supported languages, kept current with every release, and used directly for FDA and MDR submission reviews
11 years of continuous collaboration, the engagement expanded beyond Elvie Pump to Elvie Stride and additional product lines
26 months of initial development delivered in coordination with Elvie's hardware team
CLIENT’S TESTIMONIAL
KEY TAKEAWAYS
BLE abstraction layer pays off
Writing one interface that normalizes device communication means new variants can be added without rewriting session management, data sync, or UI logic.
Go for hardware-in-the-loop automated testing
Real devices controlled by an Arduino running a test rig were the only practical way to sustain regression coverage for a physical medical device across iOS and Android simultaneously.
Automate your compliance docs
Building a screenshot-generation system into the CI pipeline meant up-to-date validation artifacts ready for FDA and MDR reviews.
Start mobile and hardware teams in parallel
It is what makes simultaneous hardware/software development viable. Joining Elvie in 2019 at the hardware conception stage meant the abstraction layer design could influence the BLE protocol spec.
THE DEVELOPMENT TEAM
About the Development Team:
The project was delivered by a cross-functional team of 5 core members, including senior iOS and Android engineers, a QA specialist focused on hardware-in-the-loop testing, a UX/UI designer, and a project manager responsible for delivery and coordination with Elvie's hardware team from kickoff through ongoing release cycles. The team expanded at key phases, particularly during the Elvie Stride integration, and contracted during maintenance windows, scaling with the product roadmap rather than maintaining a fixed headcount.
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Need a Mobile App for Your Medical Device? We design, build, and ship companion apps, handling BLE communication, regulatory compliance, and automated QA.
I'm Piotr Zając, Healthcase Director at Monterail, here to answer all your questions.
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