wristsavr — forces you to take a break.
wristsavr saves your wrists: it periodically zwrites & xlocks your screen to remind you to take a 2 minute break. This is a little ditty that I whipped up last night to avoid working on my operating system.
usage: wristsavr [-hb] [-m mins] -h Display usage information. -b Bully mode. If xlock terminates before two minutes, xlock the screen again. -m mins wait mins minutes between wristsavr notices (defualt 45)