Time Out - Break timer with micro-breaks for Mac OS X.
Workrave - Workrave is a program that assists in the recovery and prevention of Repetitive Strain Injury (RSI).
Breaktime - Break time is an app that reminds you to stand up every chosen amount of time.
Eye Break - eyeBreak is a tiny app designed to sit in the Windows tray and provide a non-ignorable message...
Eyeleo - EyeLeo is a handy PC application that reminds you to take a break for your eyes.
StretchMinder - Work break timer with guided movement & breathing exercises