A phone has good optics and a built-in microphone, yet long-term streaming stresses the battery, thermal management and mobile operating system. For temporary monitoring or a secondary room it can be economical; for a critical entrance, a dedicated PoE camera is usually more predictable.
If the mobile app exposes RTSP, SmartVision can monitor and record it alongside ordinary IP cameras. The advantage is interoperability: the VMS does not need to know whether the stream originated from a dedicated camera or a phone. See RTSP Camera and Home Camera Security.