RestTimerX

RestTimerX is a utility for Mac OS X that reminds you to take breaks from typing, at intervals you specify.

It operates in a similar way to Kensington MouseWork's "Rest Reminder" feature however, since the current beta version of MouseWorks for Mac OS X is missing "Rest Reminder", I decided to write my own replacement.
What's new in this version:
RestTimerX now uses a big, translucent red banner (always on top, can't be hidden) to remind you to take a break, rather than the regular alert box of v1.0d1 . It does not actually prevent you from working, though, so you can still save that document you were working on; and since it's translucent, you can still read onscreen documents while resting. But it's a pretty annoying banner! Hopefully it's annoying enough for you to actually stop working!
The banner also features an onscreen timer...