I have been suffering from a back problem these last few weeks. I remembered that long time back in Gnome I used to use a Typing Break where the computer would force me to take a break of 3 mins every one hour. These timings can be configured to whatever one pleases.
This can be accessed from :
System->Preferences->Assistive Technologies->Keyboard Accessibilty->Typing break
Hope this helps someone who wants to take forced breaks.