Many people have used what we affectionately refer to as "Moonie Tape" Ken McNeill of Blue Moon Kites I guess was the first to use it or the first to get the word out on it. Steve sells it here http://www.chicokites.com/store/index.php?act=viewProd&productId=255
It's clear and good for flat surfaces but won't conform to odd shapes easily.
Others have used Gaffers Tape, a cloth backed black tape used in the entertainment industry for stage setup, I have seen it available at hardware stores to, a bit pricey but it has a pretty aggressive adhesive which holds well and lasts a pretty long time before needing replacement. Better for uneven surfaces since it has some flexibility and will conform better.
One member swore by Plasti-Dip which is used to give a rubber like coating to tool handles and is also available at hardware stores. He treated the nose of every kite he had with it. As I recall he started using it after wearing through a nose and doing a repair which he then covered with the Plasti-dip to make it less obvious and found it added good protection, it is pretty tough. Probably best for surfaces like the nose with its compound curves, lumps and bumps. Don't dip, just paint it on, you may need to add an appropriate solvent to thin it so it will work into the fabric.