Currently no file transfer example available.
However we have DFU (Device Firmware Update) example, where we transfer hex/binary file to the nRF51 and use that file to update the firmware on the nRF51.
You can have a look at the nRF Toolbox app.
Besides , we have the nRFUart app where we tranfer UART data from phone to nRF51 and vice versa. You can modify that app to send your own data, a file content for example.
