Look at www.nodo-domotica.nl. They are exactly what you're describing.
Except that this method is not a good idea to control lights and sockets. This sort of setup is unreliable and has all sorts of limitations. It's basically the X10 of the 1990's, reimplemented poorly. Of course there are all sorts of alternatives that have been developed, like ZWave and Zigbee. But they're not DIY projects.
For 10$ or under, you can buy an off the shelf 433 mhz setup from cheap suppliers.
There are literally thousands of people who try to build their own, and the result is usually of the quality as described in the linked article. What this woman is doing (turn AC on and off through cutting off power) will wreak havoc on her AC as it will turn off all the circuitry AC's have to gradually control temperature. She notes this as a 'todo' in her description, which is roughly equivalent to saying 'yeah I build this soap box car and I ran it down the hill, now all I need is to put in pedals and then I can go off racing Nascar'. Uh, no, not even close.
Look, I see the appeal in building something yourself, but not in something that is both as simple and ill-functioning as this - what's the point of building something badly that you can buy COTS from any hardware store for only slightly more than what she spend on this thing? Internet-enabled remote controls for AC's can be bought for 75$ or less, and they interface with the circuitry of the AC directly and let you control temperature set point, fan movement and everything else without putting undue stress on the machine.