For use with their upcoming digital M camera, Leica's announcing a 6-bit encoding scheme for all new M lenses. Each lens will have a unique 6-bit code that will be recognized by the M camera, which can be used to identify the lens and optimize image quality. The M camera will also store that information into image metadata for easy reference in image editing applications.
All new lenses from Leica will support this new code, but if you've got a supported current or discontinued lens (check the list to see if you do), you can get an authorized Leica dealer add the code on your lens for 95 Euros ($120). You'll probably want to wait until after the World Cup, since most dealers may be "busy".
Leica M lenses coding for digital [Digital Photography Review]