MathTutor5 has a built-in Clock with Alarm features.  The student will be able to preset his/her elapsed time and work on the problems of MathTutor5.

For Example, a parent may ask the student to work for 30 minutes everyday on MathTutor5.  The student simply sets the alarm for 30 minutes and begins work.  When 30 minutes has elapsed, a visual and sound message will alert the student to this fact.