I am strongly becoming addicted to SO. And I love my reputation score so much I would like SO to inform me of every change to my score that happens, via e-mail in real-time.
Believe me, you don't really want this.
If you are up to speed, you can expect 20 or more emails each day.
Better check the site every now and then.
Or if you really want a notification, maybe there is a desktop app that warns you with every change. (Maybe a red flashing light on your desktop). Or make it play a sound (happy for upvote and sad for downvote).
But, then again, you don't want to know if your rep has changed, you want to know if there is an opportunity to change your rep. So maybe a notification if a question with one of your favored tags is posted would be nice.
Just be careful what you wish for.
I would look for an application on http://stackapps.com that can do this for you!