The Center for International Maritime Security (cimsec.org) has a story on development of an Unmanned Surface Vessel. It is based on an 11 meter RHIB. (Actually in this case it looks like the Israeli firm engineered the system and the USN, BAE, and Lockeed engineered the labels, signs, and advertising.)
Still a similar system might be useful for the Coast Guard. It could provide another radar and electro-optical unit remote from the (or shore station) that launched it. It can be kept on scene longer than a manned boat, because operators can be cycled through on watches periodically, and get rest, sleep, and hot meals, rather than either being exposed in a small boat for long periods or having to return to the cutter for crew change.
This provides an additional search unit increasing the area searched by a cutter in the same way a helicopter does. It is not as fast, but more persistent and cheaper to operate.
Chuck Hill's CG Blog 
Chuck:
The Coast Guard would find USV a very capable tool for search and rescue, surveillance, and as a complement to the aging cutters’ fleet. However they have no budget for it. They are just about to integrate UAV into their operations, ten years after the Army/Navy/Air Force. USV are not closed to being purchased or even tested by the CG at this time.
The Navy doesn’t have these on anything more than an experimental basis right now either, so yes we are probably at least a decade away from an operational capability, but we need to think long term.
The USV is a great idea if your only mission is surveillance or search – or to perform the missions set out in the linked article for the USN. You can’t execute a L/E boarding or a very effective rescue at sea using a USV.
Given the CG’s crying need for manned surface assets, looking at a USV is pure folly.
I was thinking more in terms of an optionally manned vessel. One you can put a crew on when you want or send it off for extended surveillance without wearing out your boat crews.
That would be something useful…..
Singapore, which has a lot of money, but not a lot of people is already putting unmanned vessels in a Coast Guard role. http://www.navyrecognition.com/index.php?option=com_content&task=view&id=3308
Looks. Like they claim a USV can do ASW and MCM in addition to CG peacetime missions. http://www.defensenews.com/story/defense/naval/2016/02/08/israels-elbit-unveils-usv-anti-sub-anti-mine-missions/80001006/
A look at the future of Unmanned Surface Vessels. http://www.thecipherbrief.com/article/tech/one-if-air-two-if-sea-unmanned-surface-vehicles-1092
The Royal Navy is running a trial of unmanned surface vessels. The Coast Guard might ask to observe, or at least see the results of the trial. http://www.defensenews.com/story/defense/show-daily/farnborough/2016/07/13/pacific-24-950-unmanned-bae-systems/87023714/
A US unmanned surface vessel project http://www.marinelog.com/index.php/shipyard-news-channel/item/22458-swiftship-partners-to-develop-autonomous-special-ops-craft.html