As a teacher there has been more than one occasion when I need a quality timer. I know the my iPhone has a timer, but getting it to do intervals is a pain and being able to edit those particular intervals on the fly is not really possible. Are you in need of one too? Well I think I have the answer. You need to check out 30/30. Not only can you create a ton of custom intervals, you can control each interval by pausing, quickly add or subtract time from the timer, move intervals around and of course delete them. It runs in the background so if you have to switch apps, it will keep counting down. Also, it looks quite pleasing to the eye. Oh I almost forgot. This app is free which makes it even more worth your while. Check out the images below and you can find 30/30 here.