From Plex

Getting a Xbox Remote working

• Get an adapter to plug the Xbox remote ir-receiver to your mac's usb port. Buy one, or if you can solder, build one using parts from an old Xbox.
• download/install Xbox HID Driver
• download/install GamePad Companion
• configure keys to each button. Use the chart below for button to command mapping.

Gamepad Companion Mappings for Xbox Remote

Known Issue: Remote buttons 7 and 9 are unusable. "Button 27" should map to #9, yet has no effect. "Button 26" maps to both remote buttons #7 and #8, while "Button 25" has no effect. Thus #7 acts as a clone of #8.

Note: Do not turn Key Repeat off. The remote will not work with Plex otherwise.

Button 01: Menu
Button 02: Info
Button 03: Title
Button 04: Right Arrow
Button 05: Left Arrow
Button 06: Down Arrow
Button 07: Up Arrow
Button 08: Select
Button 09: Skip Back
Button 10: Forward
Button 11: Reverse
Button 12: Pause
Button 13: Stop
Button 14: Play
Button 15: Display
Button 16: Back
Button 17: #6
Button 18: #5
Button 19: #4
Button 20: #3
Button 21: #2
Button 22: #1
Button 23: #0
Button 24: Skip Forward
Button 25: No effect
Button 26: #7 and #8
Button 27: No effect