I’m thinking of adding some movement and door sensors and i’ve seen some cheap stuff on aliexpress, So i was thinking is there any simple recipe of building an ethernet gateway with 433 mhz added in to connect those to openhab via mqtt for example?
My first step into 433 mhz would be some Intertechno power plugs. As i have planed i will connect a 433mhz sender/receiver module to my raspi and running “rcswitch” on it. Doors and windows would be next. So i am quite interested how you are going to implement it.
I had a similar idea a year ago. However I wanted to include my Intertechno Power Plugs in my pure Homematic setup (this was before i moved on to OpenHAB). So here you will find a solution utilizing a 433mhz transmitter, an arduino nano and a homematic component: https://github.com/ThomDietrich/homematic-rcswitch-adapter
You could replace this one with an ethernet or wifi module. Should cost around 10€ to build. The ESP8266 wifi module would be great for that and the best part about it, you can even program it. This seems promising: http://randomnerdtutorials.com/esp8266-remote-controlled-sockets
You’ll just have to combine rcswitch with MQTT, available here: https://github.com/tuanpmt/esp_mqtt
I wanted to upgrade in this direction myself, keep me posted! 
I just made this last week.
Right now I use an arduino with ethernet shield, and then a 43mhz sender. The next step is to make a shield with an step-up converter, so I can being the 5v from usb up to 12v for transmitting. When it is all done, I am going to remove the ethernet shield, and just connect it directly to my server, and send serial commands over usb to it.
step up to 12V? My transmitter is okay with 5V, maybe buying one of these would make more sense for you?
going up to 12V gives more range, and double check if yours really only can handle 5v, a lot of them is marked as 5v, but the components used actually also do 12v
Ah I understand. Yes it is rated for up to 12 volts but 5v and a 17cm antenna is all I need to reach all my devices in my apartment reliably. 
Good luck with your project! Show off the results
@moskovskiy82 I would prefer a MQTT powered stand-alone device as you intended. Are you going to build something like that in the next few weeks? Would be really interested in your solution
I live in a house, and my hope is to get it to reach all rooms indoors, and all the way out to my garage too. If I can get the signal strong enough to do that,
otherwise you can still go with multiple wireless nodes I’m not sure when I will have the time to build this, still hoping for somebody to be quicker 