Chess Clock App that does not pause when put in the background? Hi StackExchange#Chess! 

I am looking to track how much time I spent "working" and "not working". I would like to use a chess clock for this. When I go away from my desk, I hit the player 1's timer, and when I get back to work, I hit the player 2's timer. 

I think I found some Android apps that could work nicely, but if I need to switch apps or lock the screen, they all pause. Is there any such app that runs in the background? I use Android

Thank you
I use pomello.

This isn't a timetracker really. It's more for those who practice the pomodoro technique. It tracks the number of pomodoros you can achieve while allowing you to also tag disruptions and keep you focused until your break. I picked this particular one because it's integrated with trello. The integration allows it to tag your work items with the number of pomodoros you've done on that work item.