Most commercial IoT gadgets operate with a central server. The only thing that would be needed is for both ends to keep their connection to the server alive. A firewall will let the traffic through as it belongs to an established connection.

Schlage's connected locks also seem to have an independent Z-wave radio. That serves to build a mesh network with similarly equipped devices until one has a connection out. The clip doesn't mention it, but the lock may already have been tapped in to the neighbor's Wifi ;-)