I have seen this almost working. It had the features you wanted but used to get stuck trying to disarm the motion detection occasionally. it was written by one of our suppliers and is no longer available. My point is that it is possible.
I have a nvr thats old, i use push notifications to my phone, these are forwarded by automate to a local automate, which then sends http request to update a virtual http sensor.
i have a andorid box behind my tv, this gives my tv a better smart tv functions, i use this to display the cctv app when a front door sensor is tripped.
My nvr sends a push notification to the app on my android device, the app then displays a nofication. I then use automate to intercept the notification and then send a http request to vera. On vera i use @therealdb virtual http plugin, which has virtual sensors.
My nvr does not send a push notification on motion stop.
But you could send a http request when you dismiss the notification if you wish
This video is a Fibaro Home Center 2 demo with a 16ch Hikvision NVR that has four alarm outputs on the back of it.
He is using 2x Fibaro Universal Binary Sensors or the Fibaro Smart Implant could be used.
So you’d need an NVR with several alarm output ports on it, to do more than one camera integration in to Vera for virtual motion sensors.
The 8ch NVR I was looking at only has one alarm output port. I’d need at least two alarm output ports.
Or some of the Hikvision cameras have their own alarm outputs on them, so you could connect a Fibaro Universal Binary Sensor directly to a camera rather than to the back of the NVR.
I have Zwave motion sensors under my two porches and connected to my synology nas. They work very well. I will probably move to something else soon, mainly because I don’t want to change batteries every year. They’re protected from rain but outside for the last two years.
I added them because animals and trees were always triggering false negatives.