In one implementation, a method for using a mobile computing device as a security system component includes receiving, from a mobile device and by a security system gateway, mobile device sensor information associated with sensor data captured by the mobile device at a premises monitored by the security system gateway; identifying, based on the received sensor information, a mobile device sensor information rule; identifying an action to perform in the mobile device sensor information rule; and automatically performing the identified action, by the security system gateway, in response to receiving the sensor information from the mobile device.