The problem
Most gym tracking apps punish people for being human. Miss a day and a streak resets to zero, which is exactly the moment someone is most likely to give up. Many also ask for an account, an email address and a network connection before they will record a single set, in a building where mobile signal is often poor.
We wanted an app we would use ourselves. Build Momentum is the result: an iPhone app built by our product studio, Digital Garage, and published on the App Store.
Design principles
We set four principles before writing any code, and tested every feature against them.
1. Reward consistency, not perfection
Build Momentum uses a weekly streak rather than a daily one. One rest day never resets it. That single design decision changes how the app feels: progress is something you build over weeks, not something you can lose in a day.
2. Work without a signal
The app is offline-first. Everything is stored locally on the device in a SQLite database, so logging a workout never depends on a connection. There is no loading state between someone finishing a set and recording it.
3. Collect nothing we do not need
There is no account. People can use the app without giving us an email address, a password or any personal data. Data minimisation is not a policy we added afterwards; it is how the app is built.
4. Make the common action fast
Logging a session takes two taps. Personal records are detected automatically, so people see their progress without doing any arithmetic.
What we learned
- Small design choices carry big behaviour changes. Moving from a daily to a weekly streak did more for the experience than any feature we added.
- Offline-first simplifies more than it complicates. With no server round trip in the core flow, the app is faster, there is less to go wrong, and there is no personal data to secure in transit or at rest on our side.
- Privacy by design is a product decision. Choosing not to have accounts removed whole categories of work: password resets, data subject requests and breach exposure.
Why it matters for clients
The same principles apply to public service apps and field tools: people use what is fast, what works where they are, and what does not ask for more than it needs. We bring that thinking to software and digital engineering for public and private sector clients, including apps for staff who work where connectivity is unreliable.