Installing Apple CarPlay and Taking It for a Spin
consumerreports.org
consumerreports.org
You don't have to buy all the sensors they bought for CarPlay to function. http://www.pioneerelectronics.com/PUSA/Car/NEX/AVIC-5000NEX.
Edit: On second thought, it looks like they're partnering with manufacturers so is Apple also providing their own version of the HW as well?
Either the manufacturers load it onto the car when its built or you can buy the standalone system itself. Apple has partnered with car manufacturers like Honda, Ford and Kia and select models will likely come with it.
Pioneer recently came out with their own standalone system with CarPlay which you could install yourself.
It would be interesting to see if they give you the options of choosing what system you want when you initially purchase your car. CarPlay vs AndroidAuto vs Other ones.