Abstract: A system for monitoring people's activity and/or health while at the same time preserving their privacy. Monitoring is accomplished by detecting state of people's electronic devices, e.g., a smart phone. When use of the monitored device deviates from an expected use an alert is automatically sent to a monitoring device. The relationships between users are optionally maintained in a social network. Privacy is strictly protected by reporting only deviations from use according to rules set by the person being monitored. Optionally an activity monitoring system receives data from multiple sources such as a home security system, IoT devices and a smartphone. The use of multiple data sources provides an improved activity monitoring system capable of distinguishing normal activity from abnormal activity that may be indicative of a physical or mental health condition. Variations in the monitored activity are used to identify potential health issues for the user.