Yeah, +1 for impact vests. I have one of these NPX impact vests.
Get one that's designed for Kiteboarding, my last life vest thing wasn't and it would always ride up under the chin... more harm than good.
They also give you a bit of extra buoyancy so if you end up ditching the kite due to lack of wind/skill, it allows you to concentrate on relaunching rather than surviving.
where can you buy this from?
Kite Addiction should be able to help you out.