Wikipedia
Xwrits
Xwrits is a Unix/ X11 software application which reminds computer users to take wrist breaks. This helps prevent them from developing or aggravating occupational diseases such as carpal tunnel syndrome and repetitive strain injuries. Xwrits periodically locks the X Window System while a brightly colored hand, alternately clenching and stretching as if in pain, is displayed to remind the user to take a break. Xwrits is highly customizable, though unlike Workrave, Xwrits can only be customized using command line options.