Trope-a-Day: Collapsible Helmet

Collapsible Helmet: It may – indeed, it does – qualify as Awesome But Impractical, but in situations in which you are, say, being shot at and as such may lose vehicular atmosphere Real Soon Now, it can also save your life.

You do have to mind your hair, though.  Or instruct your nano-enhanced hair to mind itself.  Either works.