Hi Ilker, welcome!
While we're using the 4G modem Kevin described, the eventual vehicle will use a mofi for the diversity antenna connections for wifi and 4g, letting us both create a larger wifi hotspot and receive better 4G signal.
We have an ubuntu EC2 instance running ovpn server setup with pivpn - see gitter for dropbox links to .ovpn file (invite only room for the moment.) It's running ok, and I can connect my mac laptop and other computers to it - the issue seems to be a timeout or other error when connecting from the pi over 4G. Kevin, have you tried it with a non-4G internet connection to the pi?
Once we start to get this platform doing longer missions, there will be all sorts of fun python or other controlling scripts for pushing data, and handling various situations automatically (kelp patch impact, sampling, state change on power condition, etc,)
Kevin and I hope to have this cruising the socal coast with 4g and occasional satcom only portions by this summer!
From the testing we did the other weekend with Kevin's survey ASV mini-kayak, I think we have a usb connection from pi to pixhawk working already (at least for pi querying pix.)
Almost all the basic parts have arrived - still need batteries and some preview ESCs, but things will start moving quickly soon!
48V power supply for surface and subsurface IP cameras (remote video feed via seperate p2p chinese sketch system), 12V, and 5V, with a 40A charge controller - lets us take up to 5 panels in series, the most our large costco standup board will handle.
I'm thinking propulsion pods using M200s with large 2 blade 3D printed and epoxied props, ducted with some acrylic on the outer side to prevent passing kelp from getting sucked in / wound up. These will be in about the middle of the board, with the 36" long, 4" tube housing our batteries and subsurface camera at the rear. This lets the edge of the camera set to hopefully catch the props in view, so we can tell if we're fouled remotely.
The panels only slightly overhang the board as shown - I'm working on figuring out a rail system that will not only support these outisde edges but extend to the nose and stern in such a way to hold kelp away from the hull. When hitting some of the big matts that are common out here I'm hoping to arrange that the kelp is held by the point at the bow, rather than swept up and under the rocker of the board. Maybe a script on the pi will notice when progress towards a waypoint isn't being made and perform some reversing, automatic re-routing mission plan.