I'm using MatterControl and it has such visualization. User can see synchronized animation which shows how the object is actually printed and user is able to see each path of filament put onto the layer.
It's possible to control starting and ending position so it's possible to precisely visualize each milimiter of filament even between start and end point.
MatterControl also visualizes extrude flow so if user set extrude to 150% or 200% then application shows wider "line".
All of it can be seen in 2D (from top view) and in 3D (perspective view).
There is also possible to see overlay (by transparency) and print speed (visualized by color).
MatterControl also shows non-printing moves and retraction points and their hight.