Sometimes I want to put a virtual hood over my head and get to work. Hog Bay Software's WriteRoom does this really well, but sometimes I want to do this in say TextMate.

Well, today I found the solution: Freeverse's Think. Puts a virtual hood over your head (that you can get out of easily if you have to), and forces you to focus on one app. I wish it could do a customized background picture (instead of just a customized fill color), but then there's that distraction again.