Do you often find yourself in a voice/video
call and others can't hear you because the microphone is muted?
Microphone Volume Monitor is the simple and easy to use tool you are looking for!
Just start the app, select the desired microphone whose volume you want to monitor and the application will update it's tray icon and let you know instantly if there's any sound coming from your microphone.
Battery optimization tip: when you're running on battery and not making calls, select "Stop" from the application menu.