, of the video sources 222, such as a camera 118 or 106. Each of the above identified elements may be stored in one or more of the previously mentioned memory devices, and corresponds to a set of instructions for performing a function described above. The above identified modules or programs i. e. , sets of instructions need not be implemented as separate software programs, procedures, modules or data structures, and thus various subsets of these modules may be combined or otherwise rearranged in various implementations. In some implementations, the memory 606, optionally, stores a subset of the modules and data structures identified above. Furthermore, the memory 606, optionally, stores additional modules and data structures not described above. In some implementations, the server side module 314 of the server system 164 determines that a user press is being applied on a button of a doorbell camera 106, and in accordance with the determination, sends a push notification to a user mobile application 624 executed on a client device 220. Optionally, when such a notification is pushed into the client device 220, the user mobile application 624 is automatically activated to display a user interface to receive a user response. Alternatively, in some implementations, the server system 164 detects motion or recognizes a face of a person in a field of view of the doorbell camera 106 based on video images recorded by the camera 106. In accordance with the detection or the recognition, the server system 164 sends a push notification to the user mobile application 624 executed on the client device 220 in association with the doorbell camera 106.