Ah Bernard
,
Yea, so most of everything I've said gets tossed out the window.
The antenna may work, but really you're not going to have much control, so things like live view might not apply. My only question is why you wouldn't just set the intervalometer and just let it go? Weight will be your biggest issue, so anything that adds to it won't be your friend.
Thanks for your answers Joe and all!

A friend is working exactly like that, but the control freak in me has been considering the usage of some rigs that enable to remote control the camera along 2 axis. Live view would help determine the right angular settings to get a reasonnably good framing. Hence my interest in remote control solutions over wifi.
It seems that Camranger and Camfi might work up to 40m~ in completely open conditions such as the ones above sea (I would be using the kite from a sailing boat to make things more fun...), so it may be an option. The Nikon wireless solution seems more robust, but the cost is very high and they are not compatible with the cheap camera I am considering using due to the high risk of losing the equipment at sea.
Thanks again for the many inputs!
Cheers,
Bernard