> But the innards of most of these antennas are very similar, usually dependent on a small booster antenna made by Alfa...

Marine WiFi extenders are all repackaged units based on a small handful of devices. The overwhelming majority are based on the Alfa (like The Wirie) and the Ubiquiti Bullet (like IslandTimePC and WiFiforboats). The Bullet based systems are definitely the best performers currently available.

I started with an Alfa (which I still pack in my laptop bag) but moved to a Bullet for the fixed installation on my boat. Very pleased, as are my customers who have taken the same path.

For WiFi inside the boat there are lots of options. Bob Stewart at IslandTimePC offers a lot of really inexpensive options. I spend a bit more and use Cisco Linksys WRT54GL routers. Either approach lets you run everything - Bullet and internal router - off 12VDC.

On Auspicious there is a hard-wired Ethernet connection to a switch connected to the Bullet and internal wifi for my laptop, iPhone, and iPod Touch and for Janet's laptop and iPhone all sharing one connection ashore.