I have some cable covers similar to those Kim links to, there's versions on ebay for less than a quid each. I've found they slow down the paint wear rather than stop it, I don't use them where there's a lot of rub like on the headtube, they're fine where there's less movement. What they are good for if you have a long cable run is removing the clatter.
I'm experimenting with tapes after asking a similar question elsewhere, though my intention is to cover much of a frame to avoid general chips and scrapes. It seems not all helicopter tape is the same, especially if you buy from ebay where it seems to have become a general term. The tape 3M recommend for bikes is HS 8671, it's on a backing so easier to cut to shape and can be applied wet to make positioning easier. I have a sample to play with, there's a knack to getting it perfect that I haven't mastered yet!
Another 3M product I've been advised to look at for a matt finish is Ventureshield.