Monitor dumb AC bulb state connected with multiway switches

Hi guys,

so I’ve been planning my new house, and ordering some stuff to try out (led strips, alarm/touch panels etc).
Now I’m wondering about a situation, so I’ve got the following:

We’re probably going to be using standaard (dumb) light switches and bulbs (most of them), since I want as few wireless as possible (I’m building a house, when is there going to be a better time to wire it).
However, I found a way to control them from HA, using multi-way switches, the dumb switch is still working just fine, but for the second switch, I’d use an Arduino controller Relay, reading values from MQTT.
This all should work, there are enough examples of this online, however I’m wondering, how do I get the actual state of the lights? I can’t just read the relay state, since that won’t know anything about the normal switch. I thought about using Current sensors, also connected to an Arduino, to read the state. I can’t really find a lot of good examples of this.
Does anybody have other ideas on how to do this? (I’m not going to hang light sensors in every room to monitor the light :stuck_out_tongue: ), also, in Belgium your electrical installation needs to be certified, could those current sensors pass the certification? (I’d use something like this:, would with less A needs)

(anybody who didn’t notice yet, I’m from Belgium, so working on 230V mains here)

thanks all :slight_smile: