I'd look to Swiss army knives for inspiration. Knife, screwdriver, scissors, pliers. A light. Someone said phone holder.. I'd have the phone embedded in the arm, positioned to be easy to see and access. Have the lock screen be various health stats: heart rate, Vmax, Time. Usb charging port... Be able to both charge the arm, and charge devices from the arm, maybe with a retractable cable ala cyberpunk 2077. Camera in a fingertip, ideally connected to XR glasses, so I can see behind or under things easily, able to be a microscope. Electric arc lighter in another fingertip.