This has to be one of the wildest, yet most sensible motorcycle and bicycle safety devices ever. The Hövding is basically a wearable airbag for your head. It goes around your neck like a slightly oversized scarf. Inside the collar are sensors that tell the device when to inflate, which it does with helium. The sensor has a series of gyroscopes and accelerometers and has been configured to only fire when you have an accident and not while doing standard bicycle moves like bending down or dismounting. Check out the action video:
The Hövding was designed by a pair of Swedish University students for their thesis, so perhaps one day it will actually make it into production.