Let's you know how many whisper you've missed when you was afk, as well as tellling people who whispers you how long you will be gone.
Updated for 5.3
[you] /amin 22:30
You are now AFK untill 22:30
[bob] Hey there!
[you] I'm AFK right now, and will be back 22:30
[you] /amin off
You're no longer AFK.
1 messages has been missed while you was gone.
-Ability to auto-answer to guild members who says your name in guild chat.
-Ability to auto-answer people who invites you to a group when you are AFK.