This article is from the Ergonomics and Typing Injury FAQ, by Dan Wallach firstname.lastname@example.org with numerous contributions by others.
sco and rsi conferences
UNIX (tested on SCO, SunOS, Mach; character and X Window mode)
This is a shell script that runs in the background and warns you to stop
typing, based on how long you have been continuously typing. It does not
provide exercises, but it does check that you really do take a break, and
tells you when you can start typing again.
Typewatch now tells you how many minutes you have been typing today, each
time it warns you, which is useful so you know how much you *really* type.
It also logs information to a file that you can analyse or simply print
out. The warning message appears on your screen (in character mode), in a
pop-up window (for X Windows), or as a Zephyr message (for those with
Athena stuff). Tim Freeman <email@example.com> has put in a lot of bug fixes,
extra features and support for X, Zephyr and Mach.