It would be great if one could use it in the terminal for announcing that some time intensive job is done, e.g. "apt-get dist-upgrade; urg-anim".
You can set the urgency hint using
wmctrl (needs to be installed):
some_task ; wmctrl -i -r $WINDOWID -b add,demands_attention
$WINDOWID is a variable holding the terminal window's ID. Because that's rather long to type, you can set up an alias for it in your
alias set_urgent='wmctrl -i -r $WINDOWID -b add,demands_attention'
Then you'd simply run:
some_task ; set_urgent
Of course this will do nothing if the terminal is active at the time the
wmctrl command is run.