Preview individual nodes on 3d mesh

While building up shaders I often find myself wondering if individual fragments of my node tree are working as I intended.  To this end what I'd suggest is a to be able to click on any node choose "Preview on Mesh" and a new temporary shader be produced with this node driving the Diffuse (if it's outputting RGB), or converted via a simple colour gradient (if it's outputting a single channel), and nothing on Specular, Normal etc.  I know I can do similar at the moment by connecting the node I'm interested in directly to the Diffuse of the main node but this also needs me to disconnect all other connections, the preview option would be non-destructive.