I'll start by saying I don't have any hands on experience using the ESP8266 as a stand alone uP, only as a wifi solution connected to Arduino. That said, the ESP8266 can be programed from Arduino IDE now and as I understand it it is not hard to do if you are already familiar with that environment. When I was playing with these it probably took about 4 hours of fiddling around to get a pair of them talking to turn on or off an LED with a check box on a webUI. You don't actually need to control the device from a web interface however, just have the "master" unit host a web page with a list of devices and their on/off states. all of your layout's devices would be on their own network and thus isolated from any other layout, and since it's on wifi protocol, it will play nice with other devices in the area.
ESP8266 Arduino Core Documentation
There are various ESP chips with more GPIO and such as well.
edit: As far as the coding needed, 90% could be copied from the standard hello world if all you want is an input pin on one to turn on an output pin on another.
