Nice idea, it could be quite useful. In the meantime have you seen this thread? -
It's a roof label placed as a roof accessory. I guess it could be modified to display the area as well, so it might be suitable for you.
Make sure you get the latest revision near the end.
Edit - Also I note Vfrontiers mentioned he might be updating it here
, so maybe PM him to see if he got anywhere and would be willing to share?