Question about power draw from light switches

I apologize if this is in the wrong section/wrong topic etc. ( first time posting)
I am a bit of a hobbyist/first year Electronic Engineering Student, so my knowledge isn't the best, apologies if i don't understand first time.

Apologies out of the way, there is an interesting product that you wire in, that replaces your mains light switch, it draws power off the two wires(one to mains and one to the light). I was curious how it did this as here is no neutral wire to the light switch.
My conclusions would be that they had a current transformer in series with the wiring with a small current drawn ( small enough for the light not to illuminate) and used a relay to switch between the light being on and a resistor to limit the current. Would this be a reasonable assumption?

I am looking to make a similar item that draws power in this fashion, would the power regulation on the other side require any special components? other than standard AC power regulation ( ie rectifier, smoothing cap, some sort of Vreg)
Thanks in advance for any replies!

the product in question is a LightWaveRF (**broken link removed**)

Modern Light Dimmers use "CHOPPER CIRCUITS" to control the average power of the light. You can find more about it in this linkhttps://home.howstuffworks.com/dimmer-switch.htm

Since you are a first-year student, I probably guess you haven't came across chopper circuits (I'm a 2nd Year Electronics Enginnering student and I too don't know much about them :-D). Just see the link, you'll get the idea. The main trick is that in place of voltage regulator, you use a chopper circuit.