I've seen a lot of people connecting a rotary dial to their computer and reading the numbers. The code detecting the signals from the phone is almost all from guidomax. I only modified it slightly to fit better for me. I also added the whole system for RemoteXY which makes me able to control the Arduino with a WiFi module (ESP8266-01). I also made it so that when a certain number isput in it will output "secret" messages. This could be used in real life puzzles like an escape room. I've seen it be done on YouTube, but they have messages be played out loud in the phone speaker. I didn't do this mainly because I did not own an SD card reader (to play MP3s from) that I could connect to the Arduino. (Ignore the random as messages ive put in the code to test it tho)
I'm skeptical this could help anyone else, its mainly for myself. I would assume that it is not optimised AT ALL, but oh well, it does the job. I made it more simpler than what ive seen other people doing it (probably because they did it right and I did it wrong) BUT IT WORKS!
I also use an Arduino from Aliexpress but as said, it works!
This is what I see on my phone when I connect to RemoteXY and the WiFi module (with the exception of the arrows and text explaining what's showing).
All this is basically just some junk thrown together as some first official project. I might do another version in the future where you could receive messages via the phone speaker and also start the "number checking" by lifting the phone. Before I take on that project alone, I would like to obtain an SD card reader. I have never posted to github before too so I really do have no idea of what i'm doing.