App for timing?

For instance, say i wanted to do HIIT compromising of 20 seconds on the punchbag - 40 seconds of - 20 seconds on and so for 5x or 10x

Im here incapable of fucking around with an app or looking at a timer, is there an app which will give me a "ding" or a warning in my headphones or whatever, when this is the case?

 

https://play.google.com/store/apps/details?id=com.simplevision.workout.tabata&hl=en

Tabata Timer for HIIT. Free. Designed for exactly what you want, tabata's.