Sending Sensor Data to Android Phone using Arduino and NRF24L01 over Bluetooth (BLE)
Bluetooth Low Energy (BLE) is a version of Bluetooth and it is present as a smaller, highly optimized version of the classic Bluetooth. It is also known as Smart Bluetooth. The BLE was designed keeping in mind the lowest possible power consumption specifically for low cost, low bandwidth, low power and low complexity. ESP32 has inbuilt BLE capabilities but for other microcontrollers like Arduino, nRF24L01 can be used.
[original story: Circuit Digest]