Let me first start by confessing that I am very new to IP camera integration!
I have done my research however, and would like to use proper NVRs for my recording, and use an API to playback from NVRs.
It seems Profile G also applies to NVRs (not just cameras with tiny on-board storage).
What is a good NVR system that supports Profile G to a client?
This is not an NVR that supports connecting to Profile G/S camera, but an NVR that itself has endpoints for application developers to connect to, start and stop recording and playback.