I will assume you have some internet connectivity. You will need to find a
Dynamic DNS provider. Your router probably supports a select set of DDNS providers, check your router first. After you have created a
URL which points to your router then you have a way to point to your IP address. You will have to check your DVR documentation to see what network port you access it from. Lets say you normally access it by
http://192.168.1.200 -- that says that you normally access it on port 80 (default http port). You would need to create a
Port Forwarding rule in your router to forward traffic to your DVR from the internet. It is NOT RECOMMENDED to use port 80 on the internet side of your router. Use a port number above 8000. So since (I made up) that your DVR is at IP address 200 you might use port 8200 as the internet port. To connect to your DVR you would do something like
http://MyDynamicAddress.dyns.org:8200 in the browser of your iPhone.
Although the setup is the same on YOUR router, I recommend
IP Camera Viewer app over using a browser.