I’ve bought recently a sureflap - pet door myself. I’ve done some research on how the communication is working. I could not find what protocol it uses but I don’t think the product uses zigbee. Intercepting the signals isn’t that easy too i’ll guess, so i’ve bought the hub for that. 
I’m recently start working on an app that uses the api from the hub to add support for the products from sureflap. I already control the lock state (open/keep inside/keep outside/lock both way) but i’ve just hardcoded the authorization mechanism for now.
