[R] Adding units to levelplot's colorkey

[Carlisle Thacker]

How to add units (e.g. "cm") to the color key of a lattice levelplot?

The plots looks fantastic, but it would be nice to indicate somewhere 
near the end of the color key that the values associated with its colors 
are in centimeters or some other physical units.

The only thing I find is the possibility to specify the labels so that 
one explicitly includes the units.  That leaves little flexibility for 
positioning where this information appears.  Is there a better way?