I was looking at the excellent Color Kinetics LED wall I saw at the Milan Furniture Fair:
and thinking about ambient display, when an idea popped into my head: what about an infrared LED dot matrix screen? On one hand it does come off as a kind of ironic "work that's in front of your eyes, but you can't see it" conceptual piece, such as the paintings in boxes that Art and Language did at one point. In those, there's a box and they tell you there's a painting inside it, but you're not allowed to open the box, so the painting is there, but you can't see it. On the other hand, I think that there's are legitimately interesting uses for a data panel that's only visible to technology, and yet is still within human line of sight.
Unlike wireless technology, an IR LED wall would have to be within eyeshot in order to be used. This impacts both security and it cuts down on the potential crosstalk of a bunch of wireless devices talking on the same set of channels creates. It also has the quality that it's effectively invisible unless someone wanted to see what it was broadcasting, thus moving control back into the user's sphere. The way you would access it would be to look at it through an IR-sensitive device, such as a cell phone camera (most CCDs are sensitive to near infrared). This creates a kind of effect, where your special glasses let you see information that's hidden in plain sight all around you. The ability to do that may be more comforting to people than invisible radio waves (assuming that's important).
I imagine the following situation: you're walking in a big city and there's an LED billboard that is playing some kind of ad, like one of the many giant TV billboards today. However, it also has a marker that says it's IR-enabled, so that there's a grid of IR LEDs interspersed between the visible light LEDs. When you point your IR-sensitive phone at it and look at the screen, you see that the IR matrix says that this billboard is downloading theater time information for the theaters in a 3 block radius around it. This is important for security, because you're not telling any server where you are or what you're interested in, it's just like looking at a billboard, but with a lot more information exchanged, without compromising security. While you're reading the message, it's using the flickering of the IR LEDs that spell out the message to send the data. You put the phone down and a map of the local theaters appears.
