I've written about my mild tendinitis in the past. As anyone with tendinitis who types will tell you, it's essential to run a program which reminds you to take breaks. I've recently been using Gnome's Typing Break feature. But, with the latest Ubuntu update, I found that it would lock up the screen for 5 seconds at break time without the chance to postpone. This, combined with the fact that the smallest break it allows is one minute spurred me to action.
I've since turned off Gnome's Typing Break and installed WorkRave. WorkRave is much more flexible, allowing any combination of small micro-breaks, larger rest breaks, and daily typing limits. I greatly appreciate the fact that it allows you to specify times in hours:minutes:seconds since my doctor recommends a 30 second break every 5 minutes. Another nice feature of WorkRave is that you don't have to stop working exactly when your time is up. It flashes a small, annoying sign, but doesn't lock-up the entire screen. This allows me to finish up what I'm immediately working on, then take a break.