luftdaten.info offers a very easy do-it-yourself instruction on how to build an inexpensive yet powerful particulates sensor complete with a fully functional firmware. This firmware regularly measures the particulates concentration and transmits the resulting data to luftdaten.info where it is processed and displayed on a world map. Even though most sensors are deployed in Germany you can find sensors all over the world.
luftpost is a simple program that monitors luftdaten.info sensors and notifies you via e-mail in case a particulates concentration measurement exceeds a threshold. The e-mail is nicely formatted and may contain the very same graphs that luftdaten.info offers — see below for an example. The notification can be triggered by every measurement, only when a measurement exceeds a threshold, or on changes only, i.e., once after exceeding a threshold and then after returning back below a threshold.