I have a specific use case for an old Android phone (Samsung GT-I8190N) running Android 4.1.2.
The time of old land line phones are long gone, but I occasionally find it useful to be able to call "the house" at times when the kids and wife have all left their phones somewhere where they can't hear them.
My plan was to utilise this old smartphone that I will attach to the wall, and a cheap "retro" phone handset with 3.5" minijack that plugged into the headphone port. What I can't find though is an calling/messaging app that:
works without SIM card, and is not confusing or full of advertising, so that even small children can use it - preferably open source, but should at least have a simple screen where the user can select which person to "call" (over the Internet obviously, as there is no SIM card).
supports directing the ringing tone to the speaker, while the voice audio goes through the phone handset
I'm OK with installing a server application on a Linux server to route all the calls go though, and would actually prefer that, but I'm also OK with going through a 3rd party server.
Does anyone have any tips about what Android app would fit this purpose?