A couple of weeks ago we told you about Spidi's airbag-equipped race suit. Unlike the Alpinestars and Dainese systems that are still in development, you'll be able to buy Spidi's system to use on the street in the very near future. Also unlike the Dainese and Alpinestars systems, Spidi uses a lanyard attached to the motorcycle to activate the charge, meaning the risk of accidental inflation is high and the bag may not inflate at all if the rider doesn't separate fully from the motorcycle before impact. Here's video of that system in action.
As you can see, the idea appears to be to prevent not only severe
impacts to the neck area, but also to restrict the motion of the helmet
and therefor the risk of whiplash and other similar injuries caused by
too swift motion or over flexion of the neck.