DisplayBuddy is a macOS utility that lets you adjust brightness, contrast, and volume on external displays straight from the menu bar, using DDC/CI over the existing video cable — no extra hardware required. It handles Apple Studio Display and most third-party monitors, supports global hotkeys, and reacts to ambient light if you want auto-brightness for non-Apple panels.

The app is a paid macOS download with a free trial, made by an indie team that publishes a blog and direct comparison pages against BetterDisplay, Lunar, Dell Display Manager and LG OnScreen. It's been covered by 9to5Mac and MakeUseOf, so the external footprint is real rather than SEO chatter.