add-on
discrete product or component that attaches to or works with a main item to extend its functionality
remote control
physical device used to control another device remotely (often wirelessly)
accessory
fashionable or decorative accessory to clothes or interior furnishings
battery grip
photographic equipment
wine accessory
equipment used in the storing or serving of wine
expansion card
circuit board able to be connected to a computer system to add functionality
mobile phone accessory
equipment used in conjunction with a mobile phone
plug-in
software component that adds a specific feature to an existing software application
peripheral
hardware device which attaches to a computer and provides input, output, storage or communication facilities
TV accessory
type of accessory