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. Optionally, facial recognition is implemented on device i. e. , locally on the doorbell camera 106 and in cloud e. g. , remotely in the server system 164. In some implementations, when face recognition is implemented locally, it is simplified according to local computational capability available at the doorbell camera 106.