How does air-drop detect other air-drop devices?
I thought I would share what I found in case this information can shortcut someone else's learning.

Bluetooth Low Energy is a completely different Spec than older versions of bluetooth. There are completely different APIs from Microsoft to support BT LE: https://msdn.microsoft.com/en-us/library/windows/hardware/jj159880%28v=vs.85%29.aspx

Unlike older versions of bluetooth, a BT LE "Peripheral" device (sending device) can advertise it's capabilities so that a connecting device (Also known as a "Central") can tell what the Peripheral is capable of without actually connecting/pairing with the Peripheral.

The capabilities of a Peripheral are communicated using a Generic Attribute Profile, or GATT for short. 

Per my previous question, the BluetoothDeviceInfo structure is part of the older Microsoft API for bluetooth supporting non-BT LE devices: https://msdn.microsoft.com/en-us/library/windows/desktop/aa363058%28v=vs.85%29.aspx

Also, the C# 32feet.net library to help with Bluetooth does not support BT LE.

I hope that helps someone.