That sounds like a fantastic tool. You didn’t happen to open source any of your efforts did you? I’m planning to do something like this and any head start would be greatly appreciated.
No code actually, I made it all in Twilio Studio which is their visual programming "no-code" tool for phone trees. Clunky to work with but trivial to set up and had enough functionality for this very simple application.
Obviously to make a real app out of it I would have redone it in a real programming language and made some frontends for web/Android/iOS.
Someone else pointed out https://freshbuzzer.com which looks like a real product that does the same thing.
