Valarm is an Android app that allows your device to capture a massive amount of information about the environment around you. Among the many great features of the app is the ability to export your data to Google Earth, creating excellent visualizations such as this:
The app can be downloaded from Google Play here, and you can read more about the process of exporting your data to Google Earth on this page.
To play with some sample data, Edward from Valarm has provided us this KML file
which is a sample of volatile organic compounds (VOCs) and air quality around the University of Southern California (USC) campus in Los Angeles, California. This dataset is part of the air quality study in the LA area.
For more, check out their site at Valarm.net or watch the video below which shows Valarm VOC sensor data around downtown LA and the University of Southern California campus in Google Earth: