I created a WIFI extender app by creating a MCNearbyServiceBrowser for my rear camera type and a MCNearbyServiceAdvertiser for my rear view mirror. I launch the app on an iPhone mid way between the front and the back of the 7 meter motorhome. The Rear camera app thinks that it is connecting to a rear view mirror device and the front rear view mirror app thinks that it has connected to a rear camera. Once both the MCNearbyServiceBrowser and the MCNearbyServiceAdvertiser have connected, any data from the rear camera is just relayed forward to the front rear view mirror. The front mirror can send data back to the camera to adjust the angle of the camera so that message is passed back via the relay app. All works 100% with a 7m distance with non of the devices needing more than 3.5m range. Only 3 old iPhones needed to create an effective rear view mirror.

I am going to try set up a repeater peer-to-peer device which will link with the back camera and then advertise itself as a peer-to-peer to connect with the front "rear view mirror" and just relay the data when it receives any. I have another old iPhone I can use. Hopefully a device can be both an advertiser and a receiver.