HomeKit Automation based on (dis)connecting of a device

I also have this question. Been trying to figure out a reliable way for HomeKit to trigger or set some uniquely testable condition when a device is not responding.

My goal was to show a red light if the garage lights had been left on, and no red light if the garage lights were off. If the garage lights are off, all the power to all the garage lights are off.

Is it possible that one of the many available “home” apps has an answer?

 

I'm not familiar with Homebridge however with HomeKit this is possible through a trigger, group, or automation activated by a scene. Depending on specifically what you are trying to accomplish. It easier to work from a power on state though.

So for example if you are trying to group light B which might be a smart bulb with light A which might be a chandelier (not smart) then I would replace light A switch with a smart switch/dimmer (Leviton makes hub less if you only want one). From there you can group the smart switch/dimmer of light A to B or you can make a simple on and off automation (when switch for light A is on light B do this, when switch for light A is off light B do that).

When it comes to Home Automation specifics tend to help because other people could have done what you are trying to accomplish but they would need to know exactly what you are trying to do.

 

It is possible within the Home app.
-> Automation
-> An accessory is controlled
-> Select light A, turn on, next
-> Select light B, choose the brightness and color you want
That should do it