I have written a small bash script that is uses ffmpeg to capture video from your screen and audio from your default microphone and zenity to provide a GUI. It is based on a script by metal1000x who's original script can be found here.

The script's menu allows you to select a window of your choice or to select a monitor. In this version of the script the monitor choices are hard coded. Please feel free to change the script to meet your needs.

The script now includes the the option to choice whether to include audio or not.

The script can be downloaded here

Requirements

The script requires that ffmpeg already be installed along with zenity which is used to provide the GUI.