Replacing cables sheaths?

[Craig Ruff via cctech]

Does anyone know of an effective technique to replace the sheath of a cable 
without needing to reterminate the ends? On all of the Apple power adapter 
cables I've used the plastic sheath starts to fall apart, but the adapter 
itself and the cable conductors are still useable. Something that results in a 
reasonably flexible coating that doesn't look like a horrible accident happened 
to the cable? :-)