http://inhabitat.com/2010/07/15/new-helmet-for-skiers-and-snowboarders-scans-for-brain-injuries/

The team designed a traditional ski/snowboard helmet lined with
sensors that measure acceleration. An accompanying LCD screen displayed colors
whenever the helmet experienced an impact. If the impact was mild, the screen
would display a green color. If the impact was severe, the screen would display
red.