I am working on smart home devices based on the zigbee, z-wave & wifi. I would like to make my smart home devices compatible with the google local SDK & apple home kit. For that, I would like to know how the provisioning is managed by the SDK or APP to add a device securely into the network.
With regards to Google's smart home platform, the seamless setup using Bluetooth is documented along with the rest of the developer documentation. That should answer your questions for that platform. I don't know about how Apple does it in their HomeKit platform.