I really doubt that is the point. To me the obvious thing that no one has mentioned is fashion.
Actually fashion can be such a severe problem with helmets that many people would rather risk their lives than wear one. In fact, in some countries (like Thailand), that is normal.
So when it comes to safety practicalities, the reality that has been demonstrated is that the unattractive appearance of helmets can often mean they aren't used at all. If a device like this were more accepted then that could save many lives.
My assumption has been that worrying about the unfashionable nature of bike helmets was mainly restricted to the developed world, and that people in the developing world were likely not wearing helmets because they are an added expense (above and beyond the expense of just getting a bicycle in the first place).
It is possible that airbag devices could 'save many lives' (if helmetless riders wore them), but I am not convinced that more wouldn't be saved by wearing helmets.
That said, the work on putting airbags on the exterior of vehicles to protect cyclists and pedestrians seems very promising, and I hope it comes to market soon.
What I'm saying is that +5% wearing the new device would be better than +0% who didn't wear anything because they didn't like helmets and the device didn't exist. I think it could be a lot percent actually.
The Thai people I spoke to told me helmets weren't fashionable. They also don't wear seat belts, since those aren't cool either, and those are already installed, so there is no added expense in that decision.
Actually fashion can be such a severe problem with helmets that many people would rather risk their lives than wear one. In fact, in some countries (like Thailand), that is normal.
So when it comes to safety practicalities, the reality that has been demonstrated is that the unattractive appearance of helmets can often mean they aren't used at all. If a device like this were more accepted then that could save many lives.