There are several of us that have built the kits within the last 3 months mine is installed and running as I guess are others so no results will be available untill about October of this year as to their effectiveness. there will certainly be one used in the Eastern Med. mine on the UK East Coast and the others in different locations. I guess there will be different modes of use, mine this year will be on last years antifouling simply cleaned down others may choose to renew their antifoul.
The premiss that a couple of us have adopted is that at a couple of hundred pounds sterling if they work great! if they extend the effectiveness of current antifouling systems good! if they don't work well it was worth the punt and passed a couple of winter hours building the kits and argueing the point, £200 lost not the end of the world.
The Jaycar system claims a peak current consumption of 3 Amps and either 200 or 300 mA /Hr overall so say 8 amps per day per unit. To meet this I have installed a 50 Watt solar panel which with a total battery capacity of 360 A should allow several weeks continuous running before I have to resort to charging the batteries from shore power etc, I did not want to leave my batteries on permanant charge. There are obviously other methods of dealing with powering the systems some of which are discussed in this thread. The Jaycar system does have a low voltage cut off to avoid completly discharging your batteries. The system claims to operate on putting out a pulsed discrete but broad spectrum of ultrasound which it is claimed disrupt both the cell structure of algea and prevent its attatchment thus removing the primary link in the food chain hence no secondary growth of fouling barnacles etc. That seems to be the commonly accepted mode of opperation for all the systems in use and the original research done many years ago.
Hope that answers some of your questions.