Highlander is a macOS utility designed to provide visual feedback of input device activity through an elegant, minimalist interface. Named after the iconic phrase "There can be only one!", this application excels at monitoring multiple input devices - from mice and keyboards to professional equipment like Wacom tablets and Logitech peripherals. It features a customizable, non-intrusive color indicator that shows which device is currently active, making it particularly valuable for users working with multiple input devices or in multi-display setups. Highlander offers seamless integration with macOS, complete with menubar controls and global shortcuts, while maintaining efficiency with minimal system resource usage.