Abstract: A device, system and method for personal health monitoring based on multitude-points environmental data is disclosed. a plurality of indoor sensing devices and a plurality of outdoor sensing devices may be connected to a network to allow bidirectional communication between the sensing devices and a central server, and between the sensing devices themselves, over a communication network such as the internet. According to one method of the disclosed invention, a source of pollutions may be detected by comparing the levels of pollution sensed by different neighboring sensing devices and recommendations as to how to reduce the exposure to sensed pollutants may be sent to end users.