This is a tutorial that demonstrates how to use Bluetooth Low Energy to send text from a phone to an Arduino UNO and display it on an OLED.
The following libraries are required:
https://github.com/NordicSemiconductor/ble-sdk-arduino (BLE SDK for Arduino)
https://github.com/mgcastro/SSD1306_text (Text support for OLED)
https://github.com/mgcastro/JS_nRF8001 (BLE library for development board)
You also need nRFgo Studio to program the Bluetooth chip:
And the nRF UART 2.0 Android App to send the text:
Here is the link to the tutorial: