Re: request: make-frame-visible hook

[Richard M Stallman]

      I have used the emacs irc clients Circe and Erc, which both provide
    modes to track activity in hidden irc buffers.  "Hidden" may mean a
    buffer that is not visible in any frame, or a buffer shown in a
    non-visible frame.  The irc channels with new activity are indicated in
    the mode-line.  Switching to a tracked buffer removes that buffer's
    indicator from the mode-line.

I don't think I would add an Emacs feature for the sake of this.
However, you might be able to get more or less the same result
by triggering off the arrival of output from a process or connection
and seeing which IRC buffers are currently displayed.