Zone is an application for Mac, that helps focus on work by "zoning in." It means that you forget about the whole world for a while and just work. Zone never interrupts you when you're zoned in and when you're taking a break it doesn't force you to get back to work like you were a child. When you're zoned in, it doesn't show any sort of countdown, because that makes you feel like time is passing slowly. But it shows time when you're taking a break, so you are aware that you should get back to work at some point. Plus, it tracks everything and you can view your report for past days and see what's the best time for you to work.
Mac OS X 10.6
Mac OS X 10.7