The Couch-to-5K Running Plan is an awesome interval-based training template to become a 5K runner. The disadvantage is that, especially in the early weeks, the intervals switch so often that your watch is beeping constantly.

You can use this visual, JavaScript-based timer if you are running indoors on a treadmill—and only in that case. If you're out on the road or on the trail, keep your attention focused and your eyes on your environment.

The timer is designed to run on a small device (I have a Nokia N810 internet tablet, but I expect it can run on your phone), without requiring internet access. The device can sit on the shelf of your treadmill, and it will flash the background of the page to catch the corner of your eye when it is time to switch between walking and running. Since it's visual, it doesn't get in the way of your music or podcasts.