Most Androids have a problem with BT microphone routing. This issue has been discusssed on many forums and there is no simple solution. My xperia Z , for example, will only communicate with "Voice Dialer" when using any BT microphone. There appears to be no easy way to route the audio from the BT mic to the application of my choice.
You might want to try an application called "Bluetooth Launch". This works on some Androids , but not on the xperia Z. If you find a solution which works let me know and I will be forever in your debt !