Mic Live is a custom made app which focus on delivering the lowest lag possible. Plug it into your Bluetooth speaker, Headphones, or whatever using a 3.5mm male to male headphone jack and you get a free mic.

Now by connecting your phone to output sound device (AUX, Bluetooth) you can use it as a microphone. The app also has the capability of running in the background and lets you use other apps while running the mic.