I have not put effort estimates on my tasks for a long time. Tonight, I was playing chess and saw a "notify" message come up on my Linux box that <some task> should be finished by now.
Wow - I never knew org-mode had that built-in! I ran a git-blame on the org-source code  and it's been a long time, right? I haven't tested whether it sends a Growl notification on OSX but that's really cool! (It was kinda creepy at first, though) Thanks, --Nate  https://github.com/emacs-mirror/emacs/blame/f8284f1e408b38e6a3c0e2a1d5a465fefac6800a/lisp/org/org-clock.el#L698