Re: Nice puff piece, leaves out some rather obvious questions..
"Until we have IPv6, all devices involved in house security have to go through an external server, because most home setups run NAT to offer internal devices access to the Net."
I'm not sure I follow this argument.
Scenario 1. Internal sensors, internal responders. There's no need to even get beyond the internal lan.
Scenario 2. Internal sensors, external responders, e.g. owner's phone as in this example. No need for an external server. PCs manage to go online with no external resources other then the ISPs. Why should security kit be different?
Scenario 3. Single internal sensor externally interrogated (e.g. from phone). Would need router to provide access via some specific port. Yes, as soon as you start opening the firewall you have a security risk but if that access is to a security device then you'd hope the security device is secure. Otherwise it isn't fit for purpose.
Scenario 4. Multiple internal sensors externally interrogated. Either punch multiple holes in the firewall, one for each, or, much better, a single hole to contact an internal server.
None of these scenarios require an external server. Granted 3 & 4 introduce trade-offs that some of us might not be comfortable with but not more so than an external server provided by a service company. And they're not dependant on the service provider remaining solvent.
Scenarios where external servers become essential involve one or more of marketing ("because cloud"), continued revenue stream or big data (you're not the user, you're the product). In other words they're there for the interests of the vendor and if the vendor goes out of business then the device becomes more electronic land-fill.