Doesn't say so directly but it seem as if AROs need to be "anchored" on a device (often a RFID-tag). Book mention the RFID-tag and AROs quite often. As well as Commlink and AROs. Also Every icon in the Matrix is one of six things: a persona, a device, a PAN, a file, a host, or a mark. ARO is not one of them. It doesn't have an Icon of its own, implying that you interact with a device or a file located on a device.
RFID-tag (device):
geo-tagging: Assigning AROs to a specific physical location, often using RFID tags.
Commlink (device):
You don’t have to be an expert to make an ARO. If you want to send directions to your place from the party, you can draw a line on an AR map and share it with your friends. If you want to point out a person in a crowd for a buddy, you can make an ARO highlighting that person and send it.
RFID-tag (device):
You can choose which of your AROs are seen by which people, so you can keep it private or, if you’re feeling impish, put vulgar AROs on RFID tags and scatter them around town for all to see. Of course, other people can filter out the AROs they don’t want to see, and so can you.
RFID-tag (device):
Tags are used for geo-tagging locations and objects, leaving a virtual AR message for anyone who comes by, employee tracking, access control, owner-contact information for everything from vehicles to pets, vehicle and weapon registration, and so on. They can also be used as tracking devices, periodically transmitting GPS data to the Matrix.
RFID tags are devices (p. 234) that can hold one or more files, but not much else. The physical location of a tag can be found via the Matrix (Trace Icon, p. 243). Tag data can be erased with a tag eraser (p. 441) or programmed with an Edit File action (p. 239). RFID tags have owners like all other devices, but unlike other devices a tag’s owner can be changed to “nobody.”
Commlink
As long as you have some way to allow your commlink or cyberdeck to send you visual information—such as cybereyes, eyeglasses, or goggles—then you can see the AR information the Matrix has to offer.
Image Link (working together with a commlink):
Image link: A standard upgrade, this lets you display visual information (text, pictures, movies, the current time, etc.) in your field of vision. This is usually AROs, but you can display pretty much whatever you want on it. You and your team can use it to share tactical and situational info in real time. An image link is what you need to truly “see” AR and participate in the modern world.