Interval Timer - Tabata Timer 4+

I originally got this to use for timing Fartlek runs and speed intervals. The cycles are easy to customize and provide great feedback through sound and vibration. But then I started doing interval training at home (circuit, HIIT, and technique drills). Now I could add in visual keys and create complex hour long workouts and practices. Colors, sounds, titles, intervals, rests, cycles, repeats, all are customizable on the free app. If I could add one feature, it would be either a three period cycle or a cycle start warning, so that I can do high/low/get ready or left/right/rest. If I could make one change, it would be the ability to make a one time premium purchase instead of a subscription. I would like to put some money towards the app, perhaps for new templates (like the suggestion above) or for sharing, but I am wary of subscription services over one time purchases.
That said, I now use the premium service and is has even more flexibility, to the point that I use it over even physical timers at the gym.

This app used to be good. So good. Almost too good to be true but unfortunately things have changed for the worse in very saddening ways. The Trump ads don’t bother me, as much I dislike him I couldn’t care less about his ads, but other changes are extremely frustrating. No longer can you have this app open while playing audio in another app without sound stopping every 5 seconds (due to ads apparently), no longer do timer sounds work properly when the app is open in the background and no longer do the developers seem to care at all about providing a product with some semblance of consumer satisfaction. The worst part, however, is that this is still the best app of it’s kind on the App Store. So until a better one comes along, I guess I’ll have to suffer through this one.

The app has annoying video ads as of late, but is otherwise very good.

I've been using the app for years to time and track my daily physical activity routines. However, every now and again the seller decides it's time to try and milk it a bit more, and pushes out an update that adds more aggressive ads, and it's never in the update description, of course. For instance, the December 2019 (version 4.2.1) update added video adds at the end of every routine, but the update description was "We are happy to introduce a new in-app purchase to let you remove the Ads. Removing the Ads is just an option for those users hope to remove it and not mandatory. It doesn't change the way you used Interval Timer before. Just grab what you need. This new version is worth you update because we also fixed some bugs to make it more stable."

It is possible to circumvent the video ads by turning off cellular data for the app and disconnecting from WiFi, but it's far from ideal.