It's called the Bumpair. We receive a history of the development of this invention at Core 77. An early version was paired with a scooter rental company that stored one of these self-inflating helmets with each bike. Checking out a scooter on an app triggered the helmet's inflation.
The new version is available for individual consumers. You can inflate it by mouth or hand pump when needed. I realize that it sounds like you're wearing a pool float on your head, but the Bumpair 2.0 passes Europe's official safety standards for bike helmets. And, of course, it looks really cool.
Photos: Bumpair