I mean juction box. I already have switches that control three lights (https://i.stack.imgur.com/Q2vZH.jpg)

The neutral wire requirement is really a killer for me, as I'm not going to rewire me entire house. There are some switches that only require the hot wire (they pass a very small load to the light, but not enough to lit up even very efficient leds).

As of the gateway I don't really care the interface. I'm prepared to write code myself or whatever is needed.