Innovative solution to track swimming workouts and develop smart training plans.

This case study highlights how the Onix sports app development team assisted our client in implementing cutting-edge technology to improve swimmers’ awareness and engagement and provide effective swimming tracking.


Team size

9 specialists






Florida, United States


Project Duration

From January 2022 to date

Business context

Like many other startups, Phlex was born out of a realization of the problem faced by swimmers. Its founders were four avid swimmers who realized that swimming lacked effective tracking and engagement. At that time, no tool would unobtrusively provide meaningful feedback. And the only way to check heart rate was to put fingers on a neck and count each beat for six seconds. It was inconvenient, inaccurate, and inefficient.

Initially, the problem was considered from the point of view of professional swimmers. However, our client realized that was a much more common problem, extending to fitness swimmers as well. So with growing demand, the founders began building the team needed to bring their idea to life.

When our client came to us, he already had a swimming training iOS app. So the Onix team was responsible for:

  • Ensuring an effective and transparent development process

  • Gathering requirements to define objectives and product scope

  • Upgrading an older iOS codebase and building an Android app from scratch

  • Creating an intuitive and appealing swimming workout app design

  • Building an Apple Watch companion tracking app

  • Providing an opportunity to collect and process the user’s data about their swim

  • Synchronizing information and data between watches and mobile app

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Who this product is for

We've created an app for professional and non-professional swimmers who want to track their dynamic workout progress, create smart training plans, and achieve great results in swimming.

The app is deeply integrated with hardware devices provided by Phlex (Phlex EDGE), Polar (Polar devices), and Apple Watch that swimmers can wear to monitor their results during training.

Phlex solves the main goal – collecting data and displaying vital metrics so swimmers can monitor and follow the progress dynamics and compare them to adjust their training with a data-driven approach.

  • Sophisticated flexible monitoring of training results

  • Tracking swimming technique and performance in a smart and convenient way

  • Hit great swimming goals using a data-driven approach


How Phlex works

We built a swimming tracker app to monitor training, set goals, and stay highly motivated. Phlex provides a streamlined experience and a sophisticated, flexible monitoring progress view to capture results and assess swims easily.


Put on a swim-tracking device

Connect the device with
a mobile app and start swimming

Track vital metrics and
get accurate results

Adjust workout plan 
to conquer even better goals

Solutions we provide

On the part of the Onix team, highly-skilled experts were committed to working on this project. The top-level requirement was to collect and analyze the swimming data and synchronize it between watches and a mobile app. The application collects and processes such user data as distance per second, speed, stroke rate, and heart rate.

That would allow swimmers to effectively and accurately track the training process and adjust the training plan with a more data-driven approach.

To build a swim training app aligned with our client's goals and budget, the Onix team offered the following solutions:

  • Setting up regular communication to deal with a transparent development process and build a valuable solution that delivers an incredible swimming training experience.

  • Providing an ability to gather and process the user’s data about their swimming training. The app now collects vital data like speed, stroke rate, and heart rate to track the results and adjust the training process with a more data-driven approach

  • Ensuring proper data syncing between watches and a mobile app that allows swimmers to monitor and track their swimming technique and performance in a smart and convenient way

  • Implementing efficient timing tracking to improve swimmers’ awareness and fully understand their training. With scientifically validated accuracy, users can track such metrics as pace, interval, distance, and SWOLF.

Design solutions provided by Onix

To help our client successfully attract and retain users, we provided required design solutions that were appealing, easy to use, and intuitive.

Our main goal was redesigning a swimming training app to make it more aesthetically pleasing with valuable user experiences. The Onix design team provided the following solutions:


Deep research and competitor analysis

To create designs that would ultimately meet our client’s requirements and satisfy end-users, we decided to analyze the fitness industry and conduct a comparative analysis of competitors. 

Deep research allowed us to learn about the target market and identify its needs thoroughly.


Modern and solid onboarding process

Since new design trends appeared, we decided to refresh the onboarding process and make it more up-to-date and uplifted. The onboarding process is a user's first impression of the app, so our designers faced the challenge of reinforcing the app’s value and increasing the likelihood of its successful adoption.


Simple and intuitive feed

Our specialists made an easy-to-use swimmer’s log of activities to show swims in chronological order. We provided access to users' training history with the ability to view related stats. Moreover, we combined the tab of calendar activities with the swimming history to filter swims by date conveniently.


Creating stunning visuals

Visuals are one of the critical points in UI design. We made some design changes to make Phlex more visually pleasing and consistent in style and colors.

We've managed to make all visual elements and interaction points to ensure the app is easy to use and aesthetically pleasing while focusing on creating valuable user experiences!

Technology stack we use








Swift UI








Android Jetpack


Navigation Component






Wear SDK


Ryan Rosenbaum

Founder & Chief Product Officer

Working with Onix has made it incredibly easy for us to develop the software products we envisioned since day 1. From the beginning, they mobilized a highly skilled team that handled and managed tasks with extreme proficiency and professionalism. Despite the unsteady footing of startup development, Onix made this such an enjoyable project to work close to.


As a result of Onix’s collaboration, our client now operates a reliable, well-performing mobile application that brings efficiency and fun to swimming workouts.

Phlex is a simple tool that enables swimmers to connect their wearable devices with a mobile app and collect motion data for accurately tracking their swimming. Using unique devices with motion data analysis, Phlex analyzes the user’s motions during training and, based on that, provides precise data about users' swimming technique and performance.

From now on, our client will change the sport of swimming by delivering an incredible training experience with real-time tracking and post-workout analytics and allowing users to enjoy every moment of their training.

Currently, the Onix team is responsible for the Android app development. We are ready to build, design, and maintain whatever innovative solutions and unique features Phlex might entrust us with.

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