One of the winning teams – and my favorite entry of all – were Lisa and Tom, who designed the Ribcap: Head protection gear that doesn't look and feel like a bulky helmet but like a standard cap. It contains materials by D3O which are soft when worn, but instantly turn solid upon impact.
From the Ribcap site, it looks like these a worn mainly by snowboarders and skiers. Can I replace my bike helmet with a Ripcap? If yes, I want one now!