Silo has a tool called Topoloy Brush.
You can use it to draw lines on a high resolution mesh and the program creates a low resolution mesh with edge loops where you drew lines. There’s a movie about it on the Silo tutorial page.
Does Blender have anything like this? If not, is there something like this planned for a future release? It looks very useful. I think it would be a great addition to the already powerful feature set.