Right now, if a window demands_attention, its name is set in bold in the
tasklist and window selector.
However, if the window is located on another workspace, you won't know about it
unless you go see in the window selector.
I could be fun and useful to do something to the window in the pager, e.g. make
the little square representing the window blink, or draw it in red, or at least
(the less fun option) draw its borders in bold ;-)