The London Evening Standard has a short story about a new bicycling helmet. It basically worn around the head like a collar, and it inflates (courtesy of stored compress gas) when electronic sensors detect an appropriate situation, probably via some accelerometers. There is embedded video in the article which shows the helmet inflating when a crash-test dummy is rear-ended by a car.
It certainly is an interesting concept, but the whole approach seems to be one of vanity: You don't have to put up with helmet hair anymore! Feel the wind in your hair! No more funny tan lines on your face from helmet straps!
Being rear-ended is not what I would consider the most appropriate demo - hitting a large hole and doing a end-over would be better, or so would sliding out in a corner.
I'm also curious about the material of construction and how it interacts with pavement. When bicycling helmets first became popular [*], they had a hard plastic shell and foam liner. Lighter weight helmets quickly evolved, in part by removing the hard plastic. This was not without issues however, as rumors quickly spread that the foam would stick to the pavement and twist the riders neck in the process, so the hard shells began to reappear. (The hard shells were rumored to bounce you head - is that really any better?) So what happens when this helmet meets the pavement?
[*] i.e., after the various bicycle racing organizations ourlawed the leather hairnets (yes, I am really old enough to remember hairnets! Nailed on cleats, too!)