Check this out.  This is only vaguely related to ambient informatics, but it is inspiring for its out of the box thinking.
There are lots of great water ideas for ambient informatics: someone at Stanford made a fountain, the height of which was driven by the Dow.  Of course, they used bootloads of clunky and complex computing resources to make this happen.  With Atmosphericon you could create the most basic D-A pump driver mechanism, and a simple script on the PC side could drive it.

What about many pumps, or many valves, each tied to a different data source?  What about pulling the color aspect from the above idea, so that each data source was easily distinguishable?  This would be beautiful!  See the water music machines of Trimpin for more valve fun.  (can anyone find me a better link?).

What about weather?  A fountain might be a nice way to indicate weather predictions.  If, as you head out the door in the morning, your fountain is running strong and high, you had better take your umbrella!