using homeseer and maybe skype for connection and a event to setup a voip call.
But then i was looking at ready solutions.
Most i found do not allow to tap into the stream but suddenly i found this doorbell :
aliexpress.com/item/2015-New-Doorcam-C9 ... 2C201409_1
only thing is that i want to know for sure what IP grade they give this, since it comes to hang at most people there homes at the front door in the rain...
Will keep you guys updated but this looks for me promising since it supports ONVIF / rstp and more protocols

And this is another model i have found :
aliexpress.com/item/Home-Security-Door- ... 6,201409_1
and here a little bit cheaper again:
aliexpress.com/item/Home-Security-Door- ... 6,201409_1
Also a video of the image from the used camera chip inside the unit that isnt even that bad if you ask me for a doorbell cam

same question asked about ip grade