Hey Rockstar!

I personally use the Seconds Pro app (available for iPhone and Android) - the paid version allows you to save workouts, input rest times, play music, and it beeps when 3 seconds remain for each interval to let you know when to switch moves. 

I suggest using the "Circuit Timer" setting - I use this even for the tabata workouts because it's just easier to control the input. 

You can also download the free version - it's the same except you can't save your workouts, which means you have to input the moves every time.

There are plenty of other timer apps, and you can also just use a good old fashioned stopwatch! 

-Betty Rocker