Concerning the Eject Helmet system. When I was in my teens, 20's and 30's racing bikes, I would have not wanted any object on top of my head under my Helmet.
In 1992 I had a major bike wreck and broke 13 bones in the wreck. They scooped my up on the back board and transported me to the Hospital with my Helmet on (taped to the back board). If you have ever had some one else try to take your rather snug fitting Helmet off your head,, it is rather painful. Your average ER Doctor has no clue how to remove a Helmet. Since my left arm was broke, my right arm was full of tubes, I could not help,, as I felt my ears being ripped off my head,, I was screaming instructions to them,,then they stopped and I heard the other Dr. tell some nurse to go to the cast room and get the "SAW" now I about crapped my bloody pants...I did not want a circular saw near my head, not to mention them ruining my expensive custom painted Shoei Helmet.
Finally they listened to me and got the helmet removed without ripping my ears off,,,,
after going through that,,, I would gladly wear an Eject system if I raced a Bike,,, not sure how appropriate it would be in a car.. the Eject system also comes in an EMT/Rescue version that would work too and not have to be worn under our helmet. Just issued to the Rescue or EMT crew (just in case)
Just my thoughts (from first hand crash experience)
Charles