Crowdsourcing Cellphones against chemical attacks

I found this article online about technology being developed to be implemented in cellphones in order to detect potentially dangerous chemicals in the air. Although it may seem to only stimulate a society that is fearful of terrorist attacks, I can see it’s practical uses. It’s detection system works to alert the person within the vicinity of the chemical and the proper authorities in the area. I can see this technology being useful to ‘map out’ the area where the chemical is located to vacate other people in the area.