The Hardware-layer sketches are built for Arduino and only if running on platform different from RPi (or on RPI but with the use-external-arduino option setted on true in the config.json file).

In this directory you'll find sender, receiver and a single-arduino-tx-rx that's a single sketch both for sending and receiving with only one arduino board.

Use the latter in production environment.

Every sketch is based on the library (RC-Switch) used to receive and send radio signal through the Arduino. This will most likely work with all popular low cost power outlet sockets, Gas sensor, PIR/Door sensors. Supported devices should have one of the following chipset: SC5262 / SC5272, HX2262 / HX2272, PT2262 / PT2272, EV1527, RT1527, FP1527 or HS1527.

Personally my advice is to use an Arduino nano with a common 433mhz radio transmitter and a 433mhz receiver. Both this modules can be bought with few euros on Ebay or Aliexpress.

better and recommended modules are this 'Super-heterodyne' RXB6:

Actually, many 433MHz circuit boards have a coil with a few windings between the circuitry and the solder pad marked ANT. The XD-RF-5V commonly available on the market has a three winding coil with a 5mm diameter. 5mm x 3 x PI accounts for almost 5cm, so the external part of the antenna should be around 12cm to come to a total length of quarter lambda.

I always find antenna's to be black magic, but for me 12cm seemed to work! Around the internet the most common antenna's length seems to be 17.3 cm.

You can even do some more spires if you want or ... if you don't want to make the antenna by yourself, just buy it somewhere.

Referring to RCSwitch library, there are generally few common kinds of outlet switches (working on a Frequency 433.92Mhz). From a 10 pole DIP switch to the one with two rotary (or sliding) switches with four setting possibilities each.

These are the recommended kind with the 10 pole DIP:

Gas Sensor, Pir Sensor, Door/contact sensor.