I have seen this in my D700 menu and just saw it again on Nikon's tech sheet for the new D4. Is this the same tech that Minolta is using to clean their sensor of dust or is it something else? How does it work and what does it do?
No it's not for cleaning dust off the sensor, although there is an anti-dust feature that basically shakes off dust.
The dust-off reference feature has you take a shot of a featureless wall, piece of paper, overcast sky. You load that image into Capture NX2 software, and it then determines where dust spots (darker areas) are, and it then can automatically fix those areas in future images you take.
It would be nice if cameras could do this processing in-camera, but I'm not aware of any that do.