I am looking for a software providing sort of a house-internal pager. Page a small message from mobile phone (using a web page) to a ESP with display and sound to a room upstairs.
Maybe using If-this-then-that or other polling/push technique.
Sounds like a good beginners project! Google for “esp8266 tutorial” and… off you go! (ps we are here to help for specific problems you might encounter). Good luck!
I know this is a beginners project 
Not my first one. But I hoped, there might be something available to tinker with…
You might set the esp8266 as a server. Use mobile phone browser to poll server IP address with message as a parameter.
Having trouble getting the kids downstairs for dinner eh? IMHO there are two ways to approach this:
- make this a specific project for this purpose only. Enough examples to host a web server on a '66 and for the sound use an el cheapo MP3 board.
- decide this is the drop that overflows your “I should built a house automation infrastructure”. I would then recommend setting up a Rapberry Pi with Node-RED for automation and MQTT for messaging and i.e. MQTT dash for phone dashbard. It’s more complicated and overkill for this project, but it will give you a decent and very easy generic infrastructure to expand to wherever your fantasy takes you.
@Jeroen_Meijer hehe, indeed, the idea was born from this specific kids, err, issue 
Currently, I am building a local webserver app on a Raspi (which has other purposes). I can access this with my mobile and submit a form. The raspi then sends desired messages to the ESPs and honk the horns, flash the LEDs and prints text on the OLED:-)
I have thought about using IFTTT, but this requires constant polling or pushing from outside the local network.
@Markus_Illenseer Been there, done that, hehe.
Since you are already building up some infrastructure, I would recommend taking the route I described under 2). Your web browser can easily create MQTT messages, as can your webserver (assuming PHP here). MQTT is really the thing to do to move commands around your home network between ESP8266’s, light switches, weather stations, EV charger, energy meters, etc. I started doing “single problem solution” projects at first and in the end it was way, way, way too complex and I moved everything to MQTT messaging. You might want to subscribe to the youtube channel of Andreas Spiess https://www.youtube.com/channel/UCu7_D0o48KbfhpEohoP7YSQ
@Jeroen_Meijer Got a prototype for MQTT running. Mosquito-Server on my Raspberry, a web page with Mosquitto-PHP Library. Runs well, I am capable of sending topics and payloads to the ESP8266-Clients, which are blinking the LED and printing stuff on the OLED.
But the PHP -> MQTT is somehow unreliable. Sometimes it needs 3 attempts until the transmission finally reaches the MQTT server.
Any experiences or hints on how to stabilize the PHP-connection to the server? (See example: https://www.wingsquare.com/blog/developing-php-client-for-mqtt-using-mosquitto-php-library/)
https://www.wingsquare.com/blog/developing-php-client-for-mqtt-using-mosquitto-php-library/
+Markus Illenseer I have used phpMQTT https://github.com/bluerhinos/phpMQTT without any problem. Using it is easy too