I have had a few questions about the GPS I use for logging my kiting sessions. Currently, I am using a Garmin Foretrex 101 pictured below.

I don't quite trust the waterproofing, so I have taken the wrist band off and put in it a waterproof pouch, which I then put in the front pocket of my buoyancy vest. If I don't wear my vest I cannot use it, so I have also purchased a Pacqua waterproof arm pouch.
If you want to get serious and try for a speed record, you can read about which GPS units to use the Navi GT31 or Navi GT11 ) is recommended, at GPS-kitesurfing.com. You can also upload your track logs to this site and compare with others how you are going.
For more information see GPS for kitesurfing - Kitesurfing Handbook
For more information see GPS for kitesurfing - Kitesurfing Handbook