The greatest disadvantage of a pi: if not power cycled properly (eg power outage), you are up for a round of travels changing corrupt SD cards everywhere.
I like the way people suggest to create a "private" wifi for the cams to connect to a "private" Router (to say blunt: an Access Point with outbound VPN connectivity to your OpenVPN server infrastructure).
But then you'll run into the "wifi" disadvantages corner: what about an outdoor cam on the far side of the house? Worst case, you are up to some kind of managed services Mesh network (eg like ASUS ones). That might cost a fortune.
I do not know your business case, but what is your compelling reason to act that a customer should pick your solution (and not for a "cloud based" like Ring system)?
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@bp2008 wrote: I wouldn't trust a chinese cam with port forwarding on, but even without port forwarding, I put it in a secured vlan. Where would I connect your "private" solution into? It won't go into my private vlan either. So prepare for an all-round works-for-all solution. In the past, someone even talked about a "fully mobile router" with 4G running on batteries-only. Then you're fully offgrid.
Just my 2c!
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