What of your mobile traffic would your ISP actually get though? Can you GeoIP a connection from a cellphone? That's probably coarse data at best right? They could probably buy the location data from the mobile carrier, but that's not something they'd get for free.

What the user was actually doing on their home VPN be largely opaque to the ISP. They might be able to make educated guesses like "this much traffic over this period of time looks a lot like somebody streaming a movie off their NAS", but that's pretty crude. I'm not sure they could really monetize that sort of data.

On the other hand home VPNs being common would probably increase the how much uploading the average user did. These sort of residential connections are almost always asymmetric because ISPs are counting on people downloading far more than they upload. By empowering users with home VPNs, the balance of upload/download might be upset in a way that isn't profitable for the ISP.

By “mobile data” I don’t mean location data, I mean your internet usage while you’re out and about. If you’re sending all that out through your home VPN, your ISP has a bigger picture of your overall internet usage, not just your home usage.

As for upload amounts, you are probably uploading less data, not more, because you don’t have to upload 100% of the data to the cloud to access 1% of it on demand.

I don't really get the full picture of what you're proposing, but would it be trivial enough to compare to just visiting a website from anywhere to see the footage? Because I think anything even slightly more complicated than that would turn off a lot of potential buyers.

I don’t know why it wouldn’t be.

If a device manufacturer could count on you having VPN access to your home network they could make it trivial to set up and use. You’d open an app or visit a URL, log in, and you’d have access.

If it's in an app, then maybe they can rely on your phone already being in the VPN. However, if it's in a website, then you have to give them access to export the footage out of your network and into their third-party servers (you can't expect the customers to configure and host an HTTP server from their network). You lose the advantage of the VPN (in this scenario) then. From a typical customer's point of view, it's better to be able to access their stuff from a website than from an app, because they can access their stuff from more devices without prior configuration. For example, they can borrow a friend's laptop to see the footage without needing to get them to install or configure anything to get into the VPN.

I think that any solution that includes a VPN is going to lose out in convenience even slightly against a solution that doesn't, and in a market where convenience and ease of use goes above all else, it would just not work.