Hoa Dinh in Alameda
"Apart from the internet/webcam, you will also probably need what is called a static-IP address. Virtually all home networking is done with dynamic IP addresses which means they can change. So if you start out with a working system you can monitor the IP address could change stopping you from connecting to your camera."
At least in the cases of Ring, Closeli, Q-see, and SkyBell, your cameras are connected to a server (with static IP address), and your mobile device communicates with the cameras via that server.
Having a static IP address is better, but not necessary.
My wired security system is connected to Q-see, and my wireless video door bell is connected to SkyBell. I can monitor the cameras and download video clip to a mobile device any time. Q-see and SkyBell do not charge subscription fee.