Facilitating the use of such devices is very widespread wireless access which should also be secured as much as possible (especially in corporate environments) so as not to inadvertently provide an easy means of accessing your internal network.
For both of the above technologies I wanted to provide a respectful shout-out to the following blog posts that provides step by step advice on securing wireless networks (includes physical security and hardening guest network access) as well as how public key cryptography should be implemented and used within IoT devices:
9 things to check after installing wireless access points by Eric Geier (Computerworld)
4.5 million web servers have private keys that are publicly known! by Paul Ducklin (Sophos Security)
I hope that you find the above posts/resources useful. Thank you.