by Mark Chaney.
Im building it for 2.4 but could have a look and nick the code for 2.5 so thanks for the link.
As for accessibility. The information presented using the hover over is additional extra helper information and so at the moment I am not taking into consideration accessibility. (I know, I should and its a bad policy not to), but for the current initial release it doesnt do many things. (Such as it doesnt (and may never) support javascript turned off)