Japan recently became the first country ever to allow automakers use rearview cameras instead of mirrors which are strikingly bad for aerodynamics. For example, Nissan BladeGlider concept already has such cameras.
Many automakers had already tried to use that technology in their projects and concepts, though they were not road-legal – for example, the first Tesla Model X prototype had such cameras though they were not allowed to be included into the production version.
Japanese Transport Bureau claims that the technology had not yet been legalized since the image quality was not good enough to replace the mirrors. USA, Europe and Canada are expected to join Japan by 2018.