Success!
Push a button on the iPhone and send a BLE bluetooth message to the Arduino UNO who forwards the request to a remote server via a commercial NB-IoT network; where the server parses the request and returns the results back to the iPhone via the same NB-IoT / BLE link.
In this case we request the load average of a remote Ubuntu Linux server '
cat /proc/loadavg' 12 times zones away. The remote server runs a Python UDP service "test app" for this "mini application" example.
BLE/NB-IOT/UDP internetworking
I think I may well be the first "maker" to do this with the Arduino UNO, and iPhone, the HM-10 BLE module and an NB-IoT shield and commercial network... but I cannot be sure!
I'm currently testing reliability. Will post the draft Arduino UNO sketch and the Python UDP test server code when finished preliminary testing. Please don't expect a polished product, as this is just a demonstration using the iPhone to send a BLE message to the Ardunio with an NB-IoT shield to forward the request to a remote UDP server and display the results back on the iPhone.
Also, I think I should include a few more "mini-app buttons" for this demo.