So, I don't financially benefit from this in any way, if anything if this becomes popular here the only way it benefits me is by getting more updates catered to this hardware, but...

Years ago I worked with military contractor and they used itronix laptops. They're watertight(rainproof), dustproof, and shock resistant laptops that do very well in extreme environments. I noticed these guys would buy them on a lease for $5k and then just basically give them away and they'd be resold for pennies.

I was considering this the other day and stumbled on this...
http://www.ebay.com/itm/112380273311

They're military grade laptops, some relevant features to oceangoing:

Daylight-viewable screen
Touchscreen
Low pixel but default large font screen
shock tested (this is more reliable with an ssd as these have in them)
certified against rain, splashes, marine environments, dust (while running) and even EMPs if you're worried about that sort of thing.
Built in GPS (Military grade. The docks allow you to attach an external antenna.)
Built in global GSM (CMDA card that does Quadband). Just swap the sim card and voila... internet.
8-hour rated batteries. (you can have the old ones rebuild or buy new on e-bay as model ix270-M)

The only real downside is that they weigh 8 lbs and the screen resolution is low. The screen resolution is a necessary trade off however. That's how they make the screen daylight view-able.

Anyway, they're SUPER cheap for what you get and I just got two. ($300). My battery seems to have about 75% of it's life left but there's no guarantee. If you can wait on a refirb it'll cost you $100 and if you want brand new about $130. If you mounted the dock somewhere reasonable then you could make good use of it as well.

I got navigatrix running on it and it works really well, gps works all on its own. I have a feeling you can upgrade the ram beyond 8 gig so I ordered 16. I'll update this post if there's interest. I also upgraded the hard drive to a 500gig ssd and it was trivial. Some extra screws and tape to carefully peel off the old drive but once you get that done it's easy to reconnect.

I haven't worked on the gsm (wwan) card yet but I have high hopes. The chip it's based on is pretty common so I don't imagine I'll run into trouble. The touch screen requires some tinkering to work right but I'll get to that and update here, again, if there's any interest in this.

Calm seas!

As promised an update.

I got everything working. All of the hardware works! The only big issue is that sound is a little tin-ey because it's coming from a magnesium case.

There were two GPS cards on mine, one connected via the gprs card (no antenna though) and another that's connected to a serial port. I assumed it was working because it found the aircard but you need to run 'sudo dpkg-reconfigure gpsd' from a terminal and then when it asks to check a particular serial port point it to /dev/ttyS2 (COM3). Then it works GREAT! Even indoors this thing got a solid lock.

The touchscreen is easy to set up. First download the first file here.. http://www.eeti.com.tw/drivers_Linux.html
Then get in a terminal and cd to /home/$yourusernamehere$/Downloads and run tar -xzvf eGTouch (hit tab and it'll auto complete)
After the file is unzipped go into the directory it created and run sudo ./setup.sh and it walks you through.
Finally, after a reboot run eGTouchU and run the calibration (linearization)

The aircard was detected right out of the box. I haven't tested connecting to the internet with it yet.

Some issues I'm working through:
Numlock is turned on at start... this is annoying if your 10-key is mapped over your keyboard.
Sound quality needs work. It sounded better in windows.

Nice, thank you for this info. I was just looking for some laptop like this and came across a dell 6400 xfr. But you finding seems more solid.