I go semi-AFK a lot, and sometimes I just don't pay attention to chat. I wanted a'wakeup' sound to play when someone needs to get my attention. So here's the mod I made for that. It's not really in development, but I figured I'd release it anyway.

Slash Commands:
/wakeup or /wu
status : Show WakeUp status.
on : Enable.
off : Disable.
phrase : Set magic word.
# : Set time interval in seconds you can get a WakeUp.
calls : List who's tried to wake you up, and how many times.
afk: Turn on AFK message.

So, for example, if I wanted the WakeUp sound to play when someone sent me'avon calling' in a whisper, I would type:

/wakeup avon calling

...and WakeUp would enable itself, watching whispers for'avon calling'. If you type /wakeup afk, and someone sends you a whisper, WakeUp will send a whisper back with this message:

I'm sorry, I'm AFK. You may send me a WakeUp message by sending me'avon calling' in a whisper.

Note that the interval is defaulted to 10 seconds, but can be changed to, say, 20 seconds by typing /wakeup 20.

Anyway, I generally keep the AFK message off, and just let my friends know my magic word. Then if I'm not paying attention and they need to speak with me they can at least try to alert me. Perhaps in the future I'll add some kind of functionality to allow the AFK message to be on only for people in your friends list, or maybe other features, but for now, this mod is'as-is'.

Keep in mind, that you will not hear WakeUp calls unless WoW is the active window. If another window is active (or WoW is minimized) then WoW will play the sound, but you won't hear it!

Installation:
To install, extract the archive into your AddOns folder, and move the WakeUp.wav file to your WoW\Data folder. WoW will not allow you to play wave files from another folder as far as I can tell. You may replace the WakeUp.wav file with anything you like, but it must be named WakeUp.wav (unless you edit the .lua of course). Oh, and the WakeUp.wav file included is just a telephone ring sound.