This is an interactive tool plugin for making poly/edge selections in
various ways. You can select polygons based on edges with broken smooth
phong shading. In edge mode, you can either select those phong break
edges, or edge loops along edges with strict regular quad grid topology,
or use some sort of live-selection mode which selects edges along a
polyline, without accidentally selecting adjacent edges, as it often
happens with the buildin live selection.