[saintfiends]

That's a nice and easy setup. Is there a similar product for wall switches/plates?

[Someone]

I recently came across https://www.kickstarter.com/projects/dobots/crownstone. Looks very good to me, but will not be on the market for a year, and the marketing may not 100% reflect reality.

I also haven't found how much power such a switch uses. It shouldn't be much, but for such devices, I think it should be tiny, way below 1W, and that is kind of hard to achieve (the electronics isn't the problem, but doing AC to DC conversion and transformed nog down may)