Third party hardware and software has been available to do this for more than a year. I have it own my Model S as do dozens of others. See this video for its operation:
This can be purchase from BearBu, who has company in Hong Kong that developed it all. See this thread.
The only issue is that it requires major surgery all over the car from what I've seen and who could someone trust to do this without causing damage or warranty issues?
I would love to have this system working with just the side cameras if I am assured the installation will be done carefully by someone who knows what they are doing...