Serial version 2.0 and later supports the Nordic UART Service (NUS) with a UUID of 6E400001-B5A3-F393-E0A9-E50E24DCCA9E.
6E400001-B5A3-F393-E0A9-E50E24DCCA9E
This service is implemented by the Adafruit Bluefruit LE UART Friend - Bluetooth Low Energy (BLE).