Ah.  This must be the underpinnings of the qjackctl patchbay!  Cool!!!!!

J.E.B.

  
Where can I get more info on jack.plumbing?  It sounds very interesting.
    

You can check out the DARCS repository: 

http://www.slavepianos.org/rd/?t=jack.*

..and read the manual: 

http://www.slavepianos.org/rd/sw/jack.*/jack.plumbing.text