The Karengo is related to the Japanese Nori seaweed - but of coarse is twice as delicious.
The first time I heard of Karengo was in a story book my son's bought home one day. Basically the story - went from the harvesting of the Karengo from a rocky shore - through to its cooking - and the family chowing down - very interesting.
Dried karengo was sent to members of the Māori Battalion in the Middle East during the Second World War - so it does have a significant cultural lineage.
Karengo is rich in iodine and protein.
More can be read here http://www.teara.govt.nz/en/seaweed/4
Karengo products can be purchased here: http://www.pacificharvest.co.nz/wawcs0135712/products.html