If you are looking to create a quiz with timer functionalities, QSM core itself takes care of that. But with this addon you get following advanced functionality for creating a timer based quiz:

Start timer automatically on a specific page number (by default it starts on the first page)
Show Stop timer button at the end of a page (by default hidden)
Two different timer styles to choose from. More coming in future
Better UI when timer is finished.
Show a warning when timer is 90% completed.