I installed the Pro Pak IV on our boat a few months ago and have been very happy with it. I plug it in when I leave the boat in the garage and the charger does everything automatic to maintain a charge. I had the cables custom cut to length so I don't have excess wires (cost an additional $15).
We used to dick around with those battery chargers but never got a full charge on all three of our batteries overnight. Now I just plug an extension cord into the charger's plug hidden in the side of my upholstery and get all my batteries charged overnight. Pretty slick and beats climbing into the engine compartment and connecting the charger to the batteries every night.
The website is http://www.culmrite.com The man who answered the phone was pretty cool and answered a lot of my questions.
There's also some other on-board chargers like Guest that are offered at West Marine. But I don't think Guest are waterproof like the Culmrite ones.