I think it is nice to have arpwatch active in pfSense this did not take much performance and you will get an mail when new devices connect to your network.
This package contains tools that monitors ethernet activity and maintains a database of ethernet/ip address pairings. It also reports certain changes via email.
Enable arpwatch, define you interface and mark “Disable 0.0.0.0” and
“Update vendors” to see the device informations.
I like to see the hostnames in the arpwatch database with fix IPs, you can do this by adding them to the DNS resolver.