The Leatt-Brace is a new protective device designed by Dr. Chris Leatt, a South African neurosurgeon. The carbon fiber/kevlar device fits between your body and your helmet, and it's designed to provide a platform for the helmet that controls its motion in a crash, thus reducing the possibility of neck injury.
The Leatt-Brace is available in motorcycle and car models, and requires no modification of the helmet or the car's seat. Dr. Leatt is a motorcycle rider, and developed the device to allow a comfortable range of motion during normal riding or racing, while providing full protection in the event of a crash.
The company's website is very informative. Check it out. Could be a viable alternative to the HANS device.