The Bell OH-58D, a military helicopter used by the USA, has an airbag to make life better in the event of a crash. A picture is on this page : http://en.wikipedia.org/wiki/Bell_OH-58_Kiowa#OH-58D

I'd never heard of such a thing in an aircraft before and I wondered if this unique to the Bell OH-58 and, if not, whether civilian light aircraft come with such an option ?