Airbags on the inside, that's what cars typically have. That's great for protecting people on the inside a vehicle. But, how about airbags on the outside, for the rest of us? Google's patented the idea for its driverless cars, with a system of inflatable bumpers that would react in the event of an accident. Sensors could detect when a collision is imminent and inflate the bags to hopefully reduce damage to anyone (or anything) involved. That said, typical airbags might not help when installed outside of the car, as any poor pedestrian that the system would aim to protect would likely be bounced off -- which doesn't sound particularly safe. Google has the answer, however: visco-elastic material.