WOOL

Wool Filler Kit from the Netherlands. Yeh, it's basically strong foam with two needles with tiny grooves placed near the tip. The grooves force the unspun wool into the woolen weave of the garment to be repaired, creating a fine felt surface.
You also get five balls of the most gorgeously coloured wool. I chose colours to patch up my navy blue cashmere sweater.
*sigh* these colours are like the sistine chapel of wool.
I have had this cashmere sweater for over ten years. I refuse to throw it away even though the arms are now so thin you can see through them. Everytime I wore it it felt like it would finally die.
The wool filler creates a felt like patch work on the weaker areas of the garment. You aren't trying to create a seamless or invisible repair - the repair work becomes part of the design.
It is so addictive and satisfying using the wool filler, as this short video proves.