I just got a hint from one of my friend to try a digital timer with the kids, as she had good experience with it. I looked what is available in app store, and there seems to be several, but I liked HopHopClock most. It was so simple to set up and when I told them about reward picture they rushed to tidy their rooms.
That was fun! Now they are eagerly wanting to see then next reward image, but I guess that I will save it to next week
Re: Children cleaned up their rooms in record time