WiFi-intercom - voice recognition, sending to everyone present via WiFi and voice playback.
Convenient for large rooms, where you can not shout to the interlocutors.

* All Android devices for communication should be in the same WiFi local area network: it is assumed that when you return to the general WiFi zone (home, office), smartphones of households or colleagues at the office automatically cling to the network, and are immediately ready to receive messages
* Enter messages in voice (or text) - and voice recognition in text
* Broadcast to everyone in the local WiFi network
* The application can be activated by voice assistant: tested in Google Assistant with the phrases: “OK, Google” and then “note to Everyone at Home”. After that, the assistant launches an application that automatically starts voice input of the message.

Settings:
* Voice recognition (speech-to-text)
* Voice playback (text-to speech)
* WiFi auto connect if not connected
* Port number (by default, you can not touch)
* Your name, for voicing the sender (and for private messages)

I suppose to use household members on smartphones, and put them on an old smartphone, which is constantly turned on in the kitchen as a “server”.
The application tries to autostart in order to be constantly ready for communication.