An open source and ad-free Tabata training interval timer.
Pick a number of sets and repetitions, the amount of time you want to exercise and rest for in each repetition, and the length of the break between sets, then start your workout.
Transitions between intervals are marked by pips on 3… 2… 1… countdowns.
Start exercising on the beep and stop on the bell (configurable).
When your workout is finished the bell will ring twice.
Has a Night mode and a choice of light themes.
Source code: https://github.com/insin/tabata_timer