Macoscope has released Focusbar 1.0 (http://focusbarapp.com/) for Mac OS X 10.6.6 or higher. It’s available for US$0.99 in the Mac App Store in the Productivity category.
This small Mac app is designed to help you focus on one task at a time. You press Start Activity, type your task and press enter. Focusbar’s window will show up on your screen from time to time, reminding you that it’s time to work on what you have planned.