I have a 30 year old nephew who is deaf. His lap top provides him with the ability to communicate with speaking people. I am always looking for ways to increase his accessibility.
The screen makes a quick flash when there is an alert sound. The flash is quick and bright. It does not create a blast of light that would offset a train of thought, but it is clear enough to be an alert.
Students who are working on computers may need to be alerted to a timer that is set. They may also need to be alerted to changes happening in the classroom.
Timers set on lap tops or tablets could be set to alert students to move on to the next task or to regroup back to their seats. Some students do not respond to sound or are hypersensitive to sound. This is a viable alternative.