To wire this up, first add:

 import XMonad.Hooks.UrgencyHook

to your import list in your config file. Now, you have a decision to make: When a window deems itself urgent, do you want to pop up a temporary dzen bar telling you so, or do you have an existing dzen wherein you would like to highlight urgent workspaces?

Enable your urgency hook by wrapping your config record in a call to withUrgencyHook. For example:

 main = xmonad $ withUrgencyHook dzenUrgencyHook { args = ["-bg", "darkgreen", "-xs", "1"] }
               $ defaultConfig

This will pop up a dzen bar for five seconds telling you you've got an urgent window.

In order for xmonad to track urgent windows, you must install an urgency hook. You can use the above dzenUrgencyHook, or if you're not interested in the extra popup, install NoUrgencyHook, as so:

 main = xmonad $ withUrgencyHook NoUrgencyHook
               $ defaultConfig

Now, your XMonad.Hooks.DynamicLog must be set up to display the urgent windows. If you're using the dzen or dzenPP functions from that module, then you should be good. Otherwise, you want to figure out how to set ppUrgents.

Irssi is not an X11 app, so it can't set the UrgencyHint flag on XWMHints. However, on all console applications is bestown the greatest of all notification systems: the bell. That's right, Ctrl+G, ASCII code 7, echo -e '\a', your friend, the bell. To configure irssi to send a bell when you receive a message:

 /set beep_msg_level MSGS NOTICES INVITES DCC DCCMSGS HILIGHT

Consult your local irssi documentation for more detail.

A common way to run irssi is within the lovable giant, screen. Some distros (e.g. Ubuntu) like to configure screen to trample on your poor console applications -- in particular, to turn bell characters into evil, smelly "visual bells." To turn this off, add:

 vbell off # or remove the existing 'vbell on' line

to your .screenrc, or hit C-a C-g within a running screen session for a temporary fix.

Rubber, meet road. Urxvt is the gateway between console apps and X11. To tell urxvt to set an UrgencyHint when it receives a bell character, first, have an urxvt version 8.3 or newer, and second, set the following in your .Xdefaults:

 urxvt.urgentOnBell: true

Depending on your setup, you may need to xrdb that.

If you'd like to configure *when* to trigger the urgency hook, call this function with an extra mutator function. Or, by example:

 withUrgencyHookC dzenUrgencyHook { ... } (suppressWhen Focused)

(Don't type the ..., you dolt.) See documentation on your options at SuppressWhen.

Focuses the most recently urgent window. Good for what ails ya -- I mean, your keybindings. Example keybinding:

 , ((modMask              , xK_BackSpace), focusUrgent)

Multiplies by ONE MILLION, for functions that take microseconds.

Use like:

 (5.5 `seconds`)