Just thought a few people may want something like this...
I wanted something that would turn on the front door light when you got home from work or the shops when it was dark - IFTTT to the rescue however not everyone in my household has IFTTT on their phones... So, lets do it based on current connected clients on the UniFi access point to detect when somebody gets home.
This is simply pulling from the UniFi controller's API - you're welcome to use this if you're using the GZ UniFi controller if you so desire however bare in mind this is more a POC right now and there is some delay due to the time it takes for the UniFi to update the controller. I ended up creating some simple IFTTT "Maker Webhooks" to do the dirty work of turning on / off the lights. As an added bonus there is a WebUI showing currently connected known devices. You can also hit http://ip:8004/test if you want to test your endpoints.
Code is here: https://github.com/michaelmurfy/unifi-ifttt - don't judge, it was a small effort by @asmallchild and myself done in a very short time tonight.
I've only tested this in Debian Linux, it is written in node.js and only has 2 dependencys (node-unifi and express).