Did you know you do not need fancy app timers in the classroom? You can just use Google! If you are using the Google Chrome browser just type for ex. "timer 30 minutes" and push enter and the timer will start. As you type you will also see the ability to timer **minutes with music which will set you up with music as the timer counts down.
If you are not using Google Chrome simply go to the www.google.com page and enter the time you wish in the Google search bar.