I would guess that the phone needs to be able to send the feed, and the head unit will need to be able to accept the feed.
I also think that sure, on the surface this seems cool, but what is the battery drain going to be sending video through wireless to the unit? Sure, on a 10-20 min drive, it likely wont make that big of an impact, or if you are the type to work in an office, and can just plug your phone in all day at work, but for me, I drive over an hour each way, I don't even stream music over LTE with out plugging in, I deff wouldn't use wireless for the carplay feed for that long. That said, if you have a short commute, or for me, if I am already in town and just going down the street, it sounds very cool to have it work wirelessly with out plugging it in, I just wouldn't expect to be able to use it for extended periods.