Please help me direct my mono-BT headset mic to a specific app - VirtualAmp
 

My goal is to use my phone as a sort of wireless voice amplifier because I teach dog training classes. I found an app called VirtualAmp which allows you to plug in a set of earphones and it will amplify sound picked up by the internal mic. I hooked up some external speakers, but I have to stand in one spot and hold my phone up to my mouth to use it. I tried to simply connect my mono Bluetooth headset but it only gives me the option to use it in calls and use the voice command app. Can anyone point me in the right direction to get my BT headset mic to replace the phone mic in this app? Thanks in advance!