Many parameters a smartphone accidentially measures are useful in monitoring the environment. We have recently discussed, how air pollution with particulate dust can be monitored with an easy ad on to the phone's camera. But there are even more subtle ways by which users can help to research and monitor environmental conditions. Another example is given by A. Overeem et.al. who track urban temperature over time in various metropole regions arround the globe. The approach is as simple as powerful: a regression over the battery temperature (that is measured by every smartphone anyway). The microphone, too, can give valuable data on local environmental conditions for an unlimited mass of individual users that participate. Sound level show noise emmission that can be located in space and time. Noise is regarded as a prime source of stress, but rather little is known about the changes that occur in different microgeographic regions. Apps like Weather Signal use thus a combination of the phone's sensors to contribute to a richer model for weather conditions. Appart from just passivly deploying the phones as sensor boards themselves, it is of course also possible to collect data from other local sources and just transmit the results via smartphone. This can be done by letting the users take a picture of some reading of a scale which can then be processed via image recognition. Or you just ask people to put in the readings or their observations into some kind of questionnaire. The fascinating thing is: since so many people in almost every country carry a smartphone, monitoring environmental conditions and changes is now possible on far larger scales than ever before.