Timer app keeps track of Activities' time in your Classroom. This app has to be launched by you manually in the Classroom in Teacher Sync mode via the Teacher Launchpad. You will be in control of the timer as you have the option to extend, pause or even reset the timing. When the countdown ends, the timer will vibrate to notify you that time is up. 

This Timer app is only accessible to you, and it will not appear on the student's view.