It is also good for making sure that I don't sit for too long. It gives me reminders to get up and stretch, get a drink of water, and generally move around.
I use a simple timer, the XPomodoro app, to help with this. The app costs money but I got it when it was free for a limited time. You can use anything, even just the timer on your phone or watch. It needs to give you an audible signal because you want to be concentrating, not looking at the time!
The app has a 30 min repeat built-in. That is all it is. I work for 25 mins and then I take a break for 5 mins. Lather, rinse, repeat till the job is done or it is lunch-time or time to go home.
I find this is attractive for jobs that I don't like doing because it is a finite time that I have to commit to it. Then I can have fun for 5 mins! Or, as I said, I use it a lot when I have to concentrate but my mind is resisting the concentration. Once I commit to the 25 mins, I find that I get absorbed in it and don't find it unpleasant. It is all just mind-games, but it works.
I don't use this for things that I enjoy doing, but I probably should. I am quite capable of sitting and spinning for more than an hour without a break. That is not good for body or mind.
I find this simple technique really easy to incorporate into my day and it helps me power through work quite effectively.