DisplayBuddy is a software that allows users to control the brightness, contrast, and volume of their external displays from their Mac. It supports various features such as creating presets, managing multiple displays, and changing display inputs. The app is compatible with most monitors manufactured in the last 10 years and supports Apple Silicon Macs. Users have praised DisplayBuddy for its convenience and effectiveness. The app can be purchased with a lifetime license and offers a 7-day refund policy.