Imagine having a shirt that senses the air quality and changes its colours and pattern as response to changes in air quality.
This is what Aerochromics is selling you. They have created a fabric that changes from black to white as the Air Quality Index changes (it starts at 60 AQI and the colour is completely reversed at 160 AQI). Depending on the salts used in the dye, the shirt can detect carbon monoxide, fine dust and smoke or radiation levels.
In practice it is a wearable sensor for air quality. The shirt sells for 500$ (the one detecting radiation costs 650$). At this price level it is not likely to become ubiquitous but I can see specific cases where it would come handy and where the cost may not be a major hurdle. Imagine the case of areas having potential high level of radiation (regions where there are uranium ore deposit) and you can see a reason for wearing it, assuming you have a need for staying in such areas...
Aerochromics is marketing their shirts as "nice to have" because they let you know the air quality in your city and you become a living-moving sensor sending a message to other citizens on the safety of their surrounding.
What interests me most is the pervasiveness of sensors. Researchers are inventing more and more ways to sense a variety of parameters and to embed these sensors in any material and any place, opening up the doors to new applications and creating a new culture and a new way of perceiving our environment.