Notifications for an accessory device are received at a mobile companion device. The notifications are directed to a notification processing application of the companion device that processes notifications intended for accessory device applications. The notification processing application determines an identifier of the accessory application for which the notification is intended, and provides the identifier to a notification display application at the accessory device, which determines user interface and display properties for the notification. The accessory device requests external (dynamic) user interface and display properties from the companion device, as needed, and upon receipt generates a notification display at the accessory device.