Droid Turbo Bluetooth Microphone with Touchless Controls? Can you use a bluetooth microphone to activate the touchless controls on the Droid Turbo? ("The "Ok Google Now" feature)
No, you cannot. It's built entirely to listen ONLY through its built-in microphones, as it can do so with minimal power drain. Activating touchless control through any normal Bluetooth headset would require that the Bluetooth headset's microphone be always listening and always transmitting to the phone, resulting in a massive power drain to both devices.

The only exception that I'm aware of is the Motorola Hint Bluetooth headset which is specifically designed for this, as it uses similar technology to the Droid Turbo and Moto X line to always listen with minimal power usage, has its own voice commands, and can tap into the Google Now voice functionality. Presumably, with time, we'll see other devices add the same or similar functionality.