As we all know, the ESP32 is loaded with features and today we will unlock the secrets of BLE on the ESP32 with Arduino IDE and build a custom Android app to read sensor data and send commands to the ESP32!
Open the attached Arduino sketch ("ESP32_BLE_UART_Demo.ino") and make sure you choose the right board (Tools / Board) and COM port after plugging in your ESP32 board with the USB cable. Upload the sketch to the board and open serial monitor.
Install the attached APK file on an Android device by emailing it or otherwise transferring it to your device. If you want to edit the app, go to Thunkable, set up and account, and import the .aia file that I've also attached.