Get Everything Done

Do you use an interval timer? If so, do you have any recommendations?

I started a thread on Music Practicing, and the author of a book on it recommends an interval timer, and practices one piece for 5 minutes, then stops and practices another piece for 5 minutes, etc. ; or practices a spot for 5 minutes and a different spot for 5 minutes - coming back to the original task, rotating.

I use a timer frequently, as Mark Forster recommends, but have never used an interval timer, but I reset the timer.