To start Microphone in Pebble Classic? There is the setting in Pebble's settings where you can replace Music with Microphone. 
However, I have not managed to start recording of voice in any mode: phone not logged in vs phone logged in with password. 
I am using Android with Samsung Galaxy G4. 
I have the latest Android in the phone. 

How can you start microphone in Pebble classic and Android?
Install Recordense application in Pebble and Recordense Light in Android. You can also tag your recordings during recording, which is useful.