Window Activity Alert
I am searching for a utility that will monitor a given X application's window and alert me of any change. This would be most useful for letting me know that something has happened in a window on another virtual desktop, where the window itself doesn't support such a feature. For example, a meta-refresh happening in a web browser, activity in a tailed log file, etc. (Actually, the Terminator terminal supports activity, so alerting a tailed a log file is done.)
I have a very crude bash script that, given a window ID, takes a screenshot of the window with xwd every second, and issues an xmessage if the screenshot differs from the last one. However, being crude, it doesn't always work.
I've had a look on Freshmeat and didn't find anything that can do this. Does anybody know if there is such a utility out there?