This is how kite pulleys should be designed!!! They can be fitted to any existing kite, but you may need to make some spliced slings to suit your particular kites bridle design. Splicing 3mm amsteel or similar line is not difficult and the loops can be hand sewn. Here is a good link on hand sewing and splice finishing. www.samsonrope.com/site_files/LockStitch_Whipping.pdf
Those pulleys look awsome. It would be a bit pricey to replace all pulleys on a kite such as an ids though($160). With this kind of pulley now on the market, any new kite design (with pulleys)that does not use them is being negligent IMO.