It would be cool if you could get notified when you get upvoted/downvoted. Users with high reputation could have the option to disable such feature. It would say on which question/answer you got (down/up)voted.
Basically you want to know when your reputation changed and why it changed.
This already exists - your reputation is updated in real-time. When you get an upvote it shows up in the header pretty much as soon as it happens.
If you hover over your profile, there is a popup detailing the posts that caused the reputation change. You can also click on the reputation to go directly to the reputation page where all reputation changes appear.
In conclusion - the feature request already exists.
There is no need for such a feature. Extra reputation, though nice, is not something that requires your attention. Unlike comments for example. Granted, badges might not require your attention either, and I personally wouldn't mind them not causing a notification. But such events happen far less frequently than reputation changes.
And it's not as if reputation changes are hard to track. Each profile has an entire tab dedicated to them in all their glorious detail. Just refresh it occasionally. Or you know what; don't focus on reputation all that much.