Volcom and Burton offer a Zip-Tech interface that zips the jacket to the pants for a solid seal. Also helps keep the jacket from riding up.
I found that a climber style harness, like the Ozone XC model, helps keep the jacket in place, and does not ride up as much as a waist harness. You can also put the waist harness under the jacket to help out, but you'll need to install a 'hook hole'. There are a few kite specific jackets out, along with some after market zip in options to help with placing it under the coat.