Software I'm trying out: DarkRoom and RSIGuard
DarkRoom - Old-school text editor that blacks out your monitor(s) and presents you with a retro green-on-black editor. It's just you and the text. Clone of a Mac program called WriteRoom.
RSIGuard - Break timer + mouse auto-clicker. You can get freeware that does the same thing, but this is the smartest implementation I've seen. The break timer attempts to wait for a pause in your activity - it has some complex algorithm to determine a break frequency that minimizes interruptions of flow. And the mouse auto-clicker (which clicks every time you stop the mouse) seems to have fewer inadvertent clicks compared to other programs I've tried. $50 - I'll probably buy this one.