If you're going to have multiple cameras, the next step is to combine them into one spherical image. Fujitsu has been doing this since 2010.[1] With four cameras, you can get the full vehicle perimeter. Other companies now offer such a capability.[2]

[1] http://www.fujitsu.com/us/products/devices/semiconductor/gdc... [2] http://www.fujitsu.com/us/products/devices/semiconductor/gdc...