I have a home network with a dd-wrt router and multiple dd-wrt access points. There are existing binding that work with other routers like Asuswrt, tplinkrouter and UniFi but they don’t work for dd-wrt. I also looked into SNMP but that was very complicated and the internal structure was based on lots of polling. I also considered making a MQTT bridges that monitored the logs for DHCP transactions and monitored all the AP wifi clients. Has anyone else looked into this?
If you go down the MQTT Route this may help
The one thing I have is the opposite, a script on my dd-wrt router that keeps track on who’s at home and calls OH API to update items based on this. But a binding might be useful as well, so if you need testers, I’m in 
Thanks for sharing that. Looks interest but for dd-wrt this would require optware and possibly storage beyond jffs. Looks like the monitoring that dd-wrt supports out of box is zabbix but that feel like overkill also not sure zabbix give the client presence notifications I want. I wanted to get to something event driven. When a client jons the network and possibly when it switches AP there should be DHCP logs. Started with rlog but but journald on the pi does not support remote logs over UDP. I think I will end up making long running SSH connections to all the APs and tailing the logs on the gateway.