It would be extremely helpful to have a widget that display in real time how many polygons are present in the currently opened place. As opposing to the CTRL + Shift + F2 menu, which allows you to check the amount of polygons rendered, this widget would take into account every polygon that exists (for example, in lighting.)
This would be incredibly useful for game optimization, to see what parts of the game are expensive on the poly count, and this allows you to make the polygon count much lower.
Seeing as polygon count can affect FPS, I think this will prove useful to a lot of people.