Commands like this are super-useful, and I use them all the time when editing LaTeX papers.

I used atchange for a long time:

http://jeffreycopeland.com/work/PDF/1996-03-atchange.pdf http://users.fred.net/tds/lab/atchange.html

And now, out of habit, my own wrapper around inotify. But more polished solutions like entr do seem the place to start now.