Blue Pie Apps use bluetooth to communicate with Raspberry Pi or linux-based devices.
Use a phone or tablet to control a Raspberry Pi, or set parameters on the Raspberry pi, only using using bluetooth (no wifi needed, no usb cable needed).

BTBerryWifi : Set the wifi network on your (headless) Raspberry Pi, using only Bluetooth. (see details)

See it in the store: iOS, Android,
or search for: BTBerryWifi , on your app store.
 

IMPORTANT:
It is necessary to first install the bluetooth python code on your Raspberry Pi (or compatible linux device).
It is Free (as in beer). And open-source.

Instructions (ReadMe) and an automated install script can be found on GitHub: RPi-SetWifi-viaBluetooth.
Or see Installation requirements on the Raspberry Pi".