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Personally I use ESP8266 or ESP32 modules for this because they are very inexpensive and you don't need an app on the phone, they can publish their own web page with your sensor information in it. If you link them to a Wifi router you can also make the link work over the internet so the phone doesn't have to be in close proximity.
I want to know in addition to that design, if I add a prox sensor circuit to output "1" or "0", how can I connect it to the Arduino and modifying the firmware, thus the BLE can output a control signal to tell the app what is the signal generated by this prox sensor. I only know some hardware and do not know what can I start to modify the Arduino code.