Fitness app development is a core service at Mercury Development: 1,500 mobile apps shipped since 1999, with fitness work for Tonal, Fitbit, and FitnessBank. We build for iOS, Android, Apple Watch, and connected gym hardware.
Your app crashes under load, notifications fail, and every release is a gamble. We take over codebases other teams built, stabilize them, and put real QA behind every release.
Full audit of code and infrastructure
Load, device, and connectivity testing
Stable releases on a sprint cadence
White-label tools cap what you can build and hold your member data. We build custom fitness apps you fully own: the code, the data, the subscriptions, and the roadmap.
Your source code and your member data
Content, community, and billing in one app
A migration plan for existing members
Your backlog grows faster than your team. Mercury Development engineers embed with your product and engineering teams, the way we work with Tonal on iOS, Android, and Apple Watch.
Engineers with 3 or more years of experience
Staff augmentation or a full project team
Two-week sprints with demo meetings
Some clients need a product built end to end. Others need one piece done well: a wearable integration, a redesign, or a QA pass before a big launch. Every service below works as a full build or as a focused engagement.
Native apps in Swift and Kotlin for training, tracking, and coaching products. This is the same work we do for Tonal and did for Fitbit.
Flutter and React Native apps when one codebase should cover both stores. You release to iOS and Android together on one budget.
Apps for Apple Watch and Wear OS, plus BLE and ANT+ links to trackers and gym equipment. Data syncs through Apple HealthKit and Google Fit.
Cloud backends that survive launch-day traffic spikes. Your team updates content, plans, and prices from an admin panel, without a developer.
Research, user flows, and screens people can follow mid-workout. We design for first-time users, so key actions never hide in overflow menus.
Functional, exploratory, and automated testing on real devices. Every fitness app we ship goes through its own QA track before launch day.
Fitness apps rarely fail at launch. They fail in week six, when workouts feel repetitive and progress is invisible. These are the features our fitness clients invest in, because they give members a reason to come back.
Steps, heart rate, sleep, and workouts flow in from Apple Health, Google Fit, and Fitbit devices. Members see all their numbers in your app instead of across three others. That same data feeds progress screens and coaching logic.
On-demand and structured video programs with Chromecast and Apple TV support. One fitness trainer app we built streams workouts to millions of users. Members train on the big screen instead of hunching over a phone.
Free trials, monthly and annual plans, and App Store and Google Play billing that members manage inside the app. Nobody emails your support inbox to cancel. Clean subscription flows protect your revenue and your store rating.
Training history, streaks, and personal records tied to each member's real data. Coaches get their own views for programs and check-ins. When people can see progress, they have a reason to stay subscribed.
Steps, heart rate, sleep, and workouts flow in from Apple Health, Google Fit, and Fitbit devices. Members see all their numbers in your app instead of across three others. That same data feeds progress screens and coaching logic.
On-demand and structured video programs with Chromecast and Apple TV support. One fitness trainer app we built streams workouts to millions of users. Members train on the big screen instead of hunching over a phone.
Free trials, monthly and annual plans, and App Store and Google Play billing that members manage inside the app. Nobody emails your support inbox to cancel. Clean subscription flows protect your revenue and your store rating.
Training history, streaks, and personal records tied to each member's real data. Coaches get their own views for programs and check-ins. When people can see progress, they have a reason to stay subscribed.
Mercury Development has shipped software since 1999 for clients from startups to Fortune 500 companies. On Clutch, that work holds a 5.0 rating across 34 verified reviews.
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Our fitness portfolio runs from startups to household names. We spent 10 years building Fitbit apps now used by more than 50 million people, and we work inside Tonal's engineering team on iOS, Android, and Apple Watch. FitnessBank ties step tracking to real interest rates, and Hit It Great pairs golf fitness with personalized coaching and performance tracking.
You do not sign up for a year of silence. Work runs in two-week sprints with a demo at the end of each one, and every phase ends with something you keep: documents, designs, or working code.
We gather requirements and turn them into a roadmap. You get a real estimate with scope, team, timeline, and cost.
User flows, wireframes, and mockups for every screen. The product takes shape on paper before code makes changes expensive.
You give feedback in review sessions and we iterate. Nothing moves to development until the flows feel right to you.
Sprint-based builds with planning and demo meetings every other week. You watch the product grow instead of waiting for a reveal.
Functional, exploratory, and automated testing on real devices. Bugs get caught before your members ever meet them.
We handle App Store and Google Play submission. After launch, the same team stays for monitoring, updates, and new features.
This is the stack behind the fitness work above. Native code where performance matters, cross-platform where budgets matter. Health data is handled to the standards regulators expect.
iOS, Android, watchOS, Wear OS, tvOS, and the web. We also ship desktop companions for Windows and macOS, as we did for Fitbit.
Swift, SwiftUI, Kotlin, and Jetpack Compose for native builds. Flutter and React Native when one codebase should serve both stores.
Apple HealthKit, Google Fit, and the Fitbit ecosystem, plus Garmin Connect, Strava, and MyFitnessPal integrations. Workouts, heart rate, sleep, and nutrition sync into your app and back out.
Bluetooth Low Energy, ANT+, and custom hardware protocols. We connect apps to trackers, heart rate monitors, and connected gym gear.
Chromecast and Apple TV playback for workout video. App Store and Google Play subscriptions, plus Shopify-connected storefronts.
We build to HIPAA, GDPR, CCPA, and SOC 2 requirements, with WCAG for accessibility. We document how every product stores, shares, and deletes data.
Mercury Development has met all the client's project goals and exceeded their expectations. The team has managed the project in detail, hit all deadlines, managed expectations, and reprioritized tasks. Moreover, they've understood the client's business and become a true partner.
Mercury Development delivered the project on time with a structured approach and strong technical expertise. The engagement resulted in higher customer satisfaction, improved retention, and better regulatory compliance. Communication was through email, messages, and weekly virtual meetings.
Development provides software integration and mobile app development for turnkey retail platforms, ensuring up-to-date functionality and system cohesion by scaling from 2–10 resources as needed. The team’s precise task breakdowns, affordable price point, and proactive reporting strengthen the partnership.
We’ve actually brought Mercury in across three totally different companies. First it was an app for car sales, then later they stepped in to fix a fire safety app that needed help, and now they’re building stuff for a valve manufacturer. Kinda shows they can jump into all sorts of industries and just get the work done.
Mercury Development consistently delivers high-quality codes that the client has never seen from a contract organization. They've not only contributed to existing features but have also led the development of new initiatives. Overall, the client is impressed with the vendor's talented engineers.
Mercury Development has helped the client with all kinds of developments and acquisition plans. They were quickly able to familiarize themselves with the business, industry, and products. The team maintains strong control of the timelines and budget but remains open to changes and client requests.
Mercury is very organised and there are no hidden surprises. They first scoped the project in detail, questioning the specification supplied as necessary. They also focussed on the success testing right from the start. I was also guided through the process so it was very straight-forward.
Mercury was awesome, they were reasonably priced, and took ownership over the project from the get-go. The code is clean, the app is polished, and they made multiple revisions very easy and at no additional charge. I would highly recommend working with them again, especially if you need an Apple TV app built with an API to your YouTube channel.
Feel free to contact us and we'll respond as soon as possible.
