The On Air Light
The on-air light will automatically turn on and off based on whether the production rack PC is streaming or recording when vMix is open.
Useless info on how it works
The light is toggled using a Zigbee smart plug. That plug communicates wirelessly through a USB adapter and its associated software, zigbee2mqtt. Additionally, a Python script acts as middleware to communicate between the adapter and the vMix instances on the network. More information about this Python script can be found in the Software & Automation section.
Zigbee is preferred over WiFi for a few reasons. Firewalls prevent most traffic coming to the Halo servers, and cloud-based products are less secure and less reliable than local ones are.
Dashboard
The Zigbee2MQTT dashboard can be accessed here. You can use this page to administer the on-air light, as well as any other devices you could add in the future, like studio lights.