Windows only: Free application EyeDefender regularly reminds you to take breaks and walks you through eye exercises to help you avoid headaches and blurred vision of the dreaded computer vision syndrome. EyeDefender is a simple program, allowing you to set breaks whenever you need them. If RSI is more of a problem for you than eyestrain, you may prefer previously mentioned WorkRave. EyeDefender is free for private, non-commercial use, Windows only.