iPhone: get Internet via Bluetooth
Pair your iDevice and Mac (Turn Bluetooth on for both devices, setup Bluetooth device, etc.)
Now go to Bluetooth Preferences. You should see your iDevice in the list of devices.
Click on the iDevice and then click the gear at the bottom of the list (next to + and -). There will be an option called "Update Services."
Click "Update Services" option AND press the the "Device" that is your computer on your iPad under the list of devices in SystemPreferences/General/Bluetooth. (Ex. on the iPad, under system preferences/general/bluetooth I have a list of 2 devices, Apple Wireless Keyboard and MBP. I press MBP to attempt to connect using the iPad)
For some reason, Updating Services makes the two connect. You'll get the two linked rings in the top left corner next to "iPad" or "iPod" or "iPhone."


There's an excellent thread in the Apple Community forums about how to do that:   https://discussions.apple.com/thread/3125423