Okay, so this device will need power. I considered running it on batteries, but it would complicate debugging wireless and other such issues, and if its going to derive its power for switching the relay it may as well also power the logic.

This device will have to turn ~240VAC into 12/18VDC and 3.3VDC, I was looking at some parts on digikey, but the cost is prohibitive on some of them, more so on the ones with dual output: [LINK]

I have however discovered some devices on Mouser that will covert 240VAC to 5VDC, they are relatively cheap, but most importantly they are safe and take up minimal space. Far safer and space efficient than if I were to attempt building my own power converter onto the board.

I'll do some more research but hopefully this will allow the Theia to run straight of of the lighting circuit of the house without the need for batteries.

Incidentally, I have now created a test jig, which I will use to easily test any prototypes I create and as a basis of what kind of light-switches are compatible.