Military.com has an interesting video here. Of course as the structure of a boat gets lighter, it can carry more, go faster, or require less power to push it at speed. This one is made of a composite honeycomb sandwich.
They claim a range of 3,000 miles, it would seem, similar unmanned remotely piloted surface vessel could be useful in extending the radar and visual horizon of our patrol ships relatively cheaply, without the complications of unmanned aircraft.
Because of the low weight, they claim fuel consumption is a quarter of that of a conventional aluminum craft.
More media photos and video here.
Chuck Hill's CG Blog 
Problem is that something that low in the water will only see a few miles if you want to use it for a visual/radar sensor.
Even at only 20 feet high the horizon is over five miles. If it is a small target (like a semi-submersible) a 10 mile sweep width might still be worthwhile if you consider it’s persistent. If the target is also 20 feet high, you can almost double that.
That might or might not be worthwhile depending on what your goal is. Guarding the approches to a harbor? Could be doable. Preventing landing of contraband over a long exposed coastline like the Pacific Northwest? Forgeddaboutit!
Looks like a Chris Craft.
I thought this was interesting in two ways. The unmanned aspect of course, but also because they are using a new structural material that could be applied to other types of boats and claiming huge savings in fuel costs.
For our purposes, operating from a ship, we would want a boat that can double as a standard manned boat.
Another project of this type being done by the Navy: http://www.ubergizmo.com/2011/07/the-blackfish-is-a-new-remote-controlled-jet-ski-the-navy-plans-to-add-to-their-fleet/