1.Introduction
In recent years we have witnessed a rapid surge of interest in novel person-based sensing devices,for example,for wellbeing,sports,safety,childcare,healthcare,and bio-surveillance[1].In parallel,an additional aspect increasingly moving into the fore-front is the mobile environmental monitoring by individual-worn sensors combined with a smartphone[2].Intelligent sensors(called smart sensors) accomplish the acquisition of an electric sig-nal from a physical property as well as the processing (and storage or communication) of measured signals,an amenity that makes them excellent personal exposure recorders.The wearable envi-ronmental sensors approach pools the recordings of environmental data (air quality,temperature,humidity,radiation,noise,etc.)together with recordings of human activity spaces[3].The latter represent the urban areas within which people move during the course of their daily activities and that can be tracked by Global Positioning System (GPS)-devices[4].