A lot of companies have improved their safety systems and they are great.
For all, who are not satisfied with their leash, have a look at the safety line setup shown below. You just have to shorten the leash and to do a loop at the bar-line on one site.
Specially for Naish kite owners, this change should be made, since it is working 100%, Naish's leash not, because it doesn't open the whole kite and then it still has power.

...the naish-system opens up well, if you set the leash high enough.
therefore, yo oughta perform one 'spral of death' with your kite, then the elastic leash should be long enough.

the system shown works good (and costs nothing) but i'd have more trust in it, when you add two rings instead of the knods and also use a stop-ball....