Many examples show how to send a command from Android to your ESP8266 to switch lights on etc.
This post shows you how to send data from your ESP8266 to your Android Phone using ESP-Basic and a self-made Android App. The App is build with App-inventor and really easy to build yourself.
All details on building the APP and source code in ESP-Basic on my weblog:
https://lucstechblog.blogspot.com/2019/ ... droid.html
PS you still have time to buy my book about the ESP32 before Christmass.
Sorry Dutch only: https://www.boekenbestellen.nl/boek/esp32-uitgelegd/9789463456814