How Hvding works - The invisible helmet for bicyclists
www.hovding.com/how_hovding_works
From the page
Saved with the link. Notes from 2007 to 2016 are mostly the page's own words, so this is probably an excerpt.
Hvding is a collar for bicyclists, worn around the neck. The collar contains a folded up airbag that you'll only see if you happen to have an accident. The airbag is shaped like a hood, surrounding and protecting the bicyclist's head. The trigger mechanism is controlled by sensors which pick up the abnormal movements of a bicyclist in an accident.