It looks useless.
But, I mean, come on programmers. This feature request was first documented back in 2009(specifically requesting custom properties be configurable on hover).
We're now halfway through 2014, and your trying to overkill the feature. Just give us what was requested more than 5 years ago.
Based on what you've provided, you still aren't offering an option to customize the tooltips ourselves. That's all your users want.
How much longer until you finally hear us?