Typeface indicates nice weather
The New York TImes Circuits section covers weather sensitive typefaces. The Dutch designers Erik van Blokland and Just van Rossum of LettError developed a malleable typeface that changes the form based on weather conditions. This would enable a person to perceive changes in the weather as they were reading their news or other information, all this done to changes in the typeface, which is being read for other content.
These tools are not innately learned but would take time and instruction to get the user to the sensing ability. This type of secondary communication (the primary channel of information expression is the information being communicated in the content that the typeface is spelling out. Those of us that use and are attuned to our computer's audible cues do not have to think there is an error in the system, but it is conveyed in an audible tone that we recognize and associate with some state of being or in condition. Changing typefaces would be another cue to the world around us.