nrf24 bluetooth image transfer
The NRF24L01+ is not a Bluetooth device. The nRF24 series itself implements its own more-or-less proprietary (but well documented and fairly simple) 2.4GHz signaling protocol.

While they can sort of "play at" being BLE devices, this is because the Bluetooth Low Energy signalling protocol itself is actually fairly simple too (and different than say the "main" Bluetooth 4.0 protocol).

So in short, the nRF24 is not the right piece of hardware for easily pairing with mobile devices.

Nordic do sell a variety of actual BLE transceiver chips, for example their nRF51 and nRF52 series, which may be more what you're looking for. I'm not sure whether they are or are not the most competitive option for BLE. IIRC, they also sell some combo transceivers that are capable of a wide variety of protocols in the 2.4GHz band.