I guess there are other options, but the IKO offers kiteboarder insurance, damn high deductible though.

(Gettin' ripped there!)
The IKO insurance covers you during your private practice. It covers Bodily injury or Property damage caused by a member while participating in the sport of Kiteboarding, Snowkiting or Powerkiting.
It covers $1.000.000 Bodily Injury and Property Damage per Occurrence, $1.000 Deductible for General Liability and $10.000 / 25.000 for Accident / Medical.
89 US / 68 Euros including USA/Canada (excluding local taxes).
65 US / 49 Euros excluding USA/Canada (excluding local taxes).
http://www.ikointl.com/kiteboarder-insurance.php