I think they are really working in the bacground because it has a timer that is used in sports. You select a workout and rest time and number of rounds. Lets say 10 seconds workout, 5 seconds rest for 20 rounds. If you get the app to background, you still hear the beep at the end of each work time our rest time between all rounds and the ending whistle at the end of all workout. If the timer is not working on the background, how can it play the sounds at the end of each round etc?