Problem is a programmable resistance like MCP41010 can only have 1mA max through its wiper, so this is an attempt to give that wimpy resistor some teeth.
what got me thinking on this was:
http://forum.arduino.cc/index.php?topic=298619.0
also found MightyWatt which is missing resistor mode (it has CC and CV, but not CR):
http://kaktuscircuits.blogspot.com/2014/07/mightywatt-revison-2-now-50-mightier.html
and an EDN article that gave some ideas:
http://www.edn.com/design/test-and-measurement/4322585/Digitally-programmable-resistor-serves-as-test-load
