Identifying entities based on sensor data

Sensor data from multiple sensors associated with a user is received. The sensors may include sensors of a smart phone, and sensors associated with other devices such as fitness trackers, video game consoles, and cameras. The sensor data is processed to identify entities such as persons, locations, and objects that may be of interest to the user. A personal digital assistant application can present information related to the identified entities to the user, and can allow the user to perform various queries with respect to the identified entities, and previously identified entities. In addition, the identified entities can be used to trigger one or more rules including recording when and where a particular entity is identified, and generating an alert when a particular entity is identified.