Time map in render window

Hello! I thinked a way to see how much each render tile needed to be rendered. I think it’s useful to understand how a scene could be improved.
The “render pass”, if it could be called so, shows the time needed for each frame, and with a background color that goes from red for longer times to green for quickier tiles.

I don’t know how much difficult could be this to be created. Is it possibile to implement through and add-on?