(I was going to write this as a note to myself, but figured I'd put it here while I digest it)

The troubling thing about pinning down the nature of ambient displays is that too many end up being displays that forcibly get your attention when they have pertinent information (like the light on the answering machine or the shaking string denoting high network activity) or they need to be polled specifically, like the 'weather mobile' or, well, a clock in general.

Really good ambient displays provide their information nondisruptively during the course of the observer's everyday tasks.

Cases in point:

A kleenex cube is a poor example of an ambient display because it gives only the binary reading of 'empty' (no tissue sticking up) or 'not empty' (tissue sticking up).

Rolls of toilet paper are good examples of ambient displays because you know how much toilet paper is left, without ever directly polling the object to find out.

The key is that most ambient displays are tightly coupled with the objects they display information about. Successful man-made displays will probably rely on representative state-changes to metaphoric representations of the relevant objects, like fluid in a cylinder indicating how full a hard drive is. The display is even more successful when the user comes across the information over the course of their user's normal activities.

That's all for now...