Make an app
Make a HIIT and interval timer app for iPhone
An interval timer is simple until you try to read it from across the room mid-burpee. Describe your rounds and Borel builds a native iPhone HIIT timer in SwiftUI with huge numbers, a colour for work and one for rest, a buzz and a spoken cue at every switch, and saved workouts for Tabata, EMOM or your own circuits.
Updated
“A HIIT timer: I build workouts from rounds of work and rest (for example 8 rounds of 20 s work and 10 s rest), with optional exercise names per round. The running screen shows huge numbers, green for work and red for rest, the next exercise, and the phone buzzes and says 'rest' or 'go' at each change.”
Screens
What a HIIT timer app needs
The screens Borel builds from the prompt above. Ask for more, fewer or different ones.
Workouts
Tabata, EMOM and your saved circuits, each with its total time.
Builder
Rounds, work seconds, rest seconds, warm-up, cool-down and exercise names.
Running
Full-screen countdown, work in one colour and rest in another, next move below.
Done
Total time and rounds, saved to a simple history.
Data
What it keeps
Borel writes these as Swift models. On the phone they work with no connection; in Borel's cloud they follow a signed-in person.
| What | Holds | Kept |
|---|---|---|
| Workout | Name, rounds, work and rest seconds, warm-up | On the phone, with SwiftData |
| Round | Optional exercise name per round | On the phone, with the workout |
| History | Date and workout finished | On the phone, with SwiftData |
Native iPhone features
What it can use on your iPhone
Written in Swift with Apple's own frameworks, so they work the way iPhone owners expect.
- HapticsA double buzz for go and a single one for rest, felt through a pocket.How Borel builds it
- Voice and speechThe iPhone's own voice says 'go', 'rest' and the next exercise.How Borel builds it
- Liquid Glass designNumbers that scale with Dynamic Type and stay readable at arm's length.How Borel builds it
Make it yours
What to ask for next
Once the first version runs, ask for changes in the chat, in words like these.
- “Count down the last three seconds of every round out loud.”
- “Keep the screen awake while the timer runs.”
- “Add a 'repeat the whole circuit' setting with a longer rest between circuits.”
How to make it
From a prompt to your iPhone and the App Store
- 1
Describe it
Paste the prompt on this page into Borel, or write your own in plain words. Borel plans the screens with you before it builds.
- 2
Try it in your browser
Borel writes the app in Swift and SwiftUI, builds it with Xcode on its own Mac and opens it in a live iPhone simulator in your browser, free.
- 3
Put it on your iPhone
With Pro, Borel Companion for Windows or Mac installs it on your own iPhone with your Apple ID: a cable the first time, then Wi-Fi.
- 4
Publish it when it's ready
Pro publishes to the App Store from the same project. Apple's Developer Program, $99 a year, is the one thing you pay Apple.
Prop your iPhone against a wall and do a full workout with it. Check that the numbers read from where you stand, that the voice cue isn't drowned by your music, and that the buzz is strong enough. Then ask for bigger, louder or longer, and the new version arrives over Wi-Fi.
Trainers sometimes give clients their own timer with their own circuits in it. Publishing with Pro puts yours on the App Store under your name, with your circuits as starter workouts.
Building starts free, with 5 free credits a day, up to 30 a month, and the simulator in your browser costs nothing. Pro, from $20 a month, adds installs on your own iPhone through Borel Companion and publishing to the App Store.
Before you start
Good to know
- When the app is in the background, it can't speak each switch; cues play while it's open, and a notification can mark the end.
- There's no Apple Watch companion to show the countdown on your wrist.
Frequently asked questions
Yes. Tabata is 8 rounds of 20 seconds work and 10 seconds rest; write that in your prompt and Borel builds it as a starter workout.
Yes. Borel uses the iPhone's built-in speech voice for cues like 'go' and 'rest'. No recordings or API keys are needed.
Ask Borel for the cues to play over your music and briefly lower it, and it sets the iPhone's audio to do that.
Yes. The countdown and colours run in the live iPhone simulator; buzzes need the real phone.
Make your HIIT timer app
Start from the prompt on this page, change it to fit your idea, and Borel builds it while you watch.