Unless Mr.Wizard is on vacation, it is pretty difficult to beat this phenomenon which seems to be gifted with omnipresence and omniscience. How can we outdo him using Mathem
Pretty easy actually. All you need is the following.
Define a watch task:
storedTitle = "";
mySOWatchTask =
CreateScheduledTask[
{
lastTitle =
"title" /. ("questions" /.
Import["http://api.stackoverflow.com/1.1/questions?key=\
QEpjCjsXYE6s_kZEkFr4Lw&page=1&pagesize=1&sort=creation&tagged=\
mathematica", "JSON"])[[1]];
If[lastTitle != storedTitle,
storedTitle = lastTitle;
EmitSound[Sound[SoundNote[]]];
MessageDialog["New question: " <> lastTitle]
];
},
60
];
And to start this:
StartScheduledTask[mySOWatchTask];
Stop it with:
StopScheduledTask[mySOWatchTask];
Look what's running:
ScheduledTasks[] // Shallow
Remove the task:
RemoveScheduledTask[mySOWatchTask];
or all tasks:
RemoveScheduledTask[ScheduledTasks[]];
This polls SO every minute (the minimum that is not seen as abusive), and displays a dialog box and a plays a sound whenever a new Mathematica question arrives.

The beauty of this is: it uses Mathematica 8, and we all know Mr.Wizard doesn't have that (yet) ;-)
Note that the SO API is being cached heavily, so response may not come directly. I also haven't tested this extensively.
EDIT
Please note that the key (app-id) used above is intended to be used by this small Mathematica application only. If you need one for a different application you can get one yourself in a fast and painless procedure here. It took me less than a minute.