The app was approved by Apple, and it is currently available for free on the Apple App Store.
I was thinking of creating a universal version of the app in the future, i.e. a version that would look differently on iPhone and iPad. However, I quite like how the existing iPhone app looks and works on iPad, stretched to full screen. I can put my iPad somewhere on a shelf, and since everything looks bigger on it, I can clearly see from a distance which interval is running now, and how much time is still left.
So my next priority is to create a similar app for Android. This is what I am working on now.