I've not had a chance to examine or test one, either. But, from the technical description I believe David is correct, i.e., the circuitry is probably based on a DC-to-DC step-up converter.
These circuits are often found on boats, from the smaller ones used with, e.g., radios to larger and quite expensive ones designed to provide 13.8VDC to a host of electronics
when the actual battery voltage is 12VDC or below.
Cute, and smart! HOWEVER, at a discount price
in the U.S. of over $400 for the 80A version, I wonder if it makes really good sense. For that money
, you can buy a really good external regulator (e.g., MC-612 or MC-614) and have some $$$ left over to put toward a much larger alternator.
IMHO, this would be preferable for those with large battery banks and, particularly, those with AGMs or gels which can put quite a strain on a small alternator. I'd much rather have a big alternator fully capable of putting out a lot of amps for a long time even when hot, rather than depend on an alternator temp sensor to keep my AGMs from burning up my small alternator being goosed by a tricky DC-to-DC converter :-)