I like snap, but seriously? Any ip camera that I know of (maybe not that many) let you change remote ports and once you forward them to the individual ip internal address you can look at them with the same app that you would use for the NVR. You probably won't be able to look at each on on a quad screen on an app but only each one at a time--disconnecting and reconnecting to each as necessary.

Icrealtime, GenIV and other Dahua products would let you do that.