I have no inside knowledge that would contradict what the support rep told you. But that’s kinda interesting, in that I believe all the other ST hubs (there are several different devices at this point that contain a ST hub) don’t have a location restriction like that.
The US v1 and v2 hubs, as well as the UK hub (equivalent to the US v2 hub) definitely don’t, although I’m not as sure about the Samsung connect home routers or the ST extend for the Nvidia shield.
Obviously the ADT-based security services will only work in an area that ADT serves. And the cellular backup connection will only function if you’re actively subscribed to ADT monitoring services.
But assuming that the rep is correct, then if you use a reliable VPN service with an exit node that’s really in the US, then I suppose that would work. If that were the only reason to subscribe to one, I’m not sure it would be worth the cost to you. But maybe the hub would continue to function with your IP address in Mexico after the initial onboarding with the US-based VPN IP address, in which case you wouldn’t have to continue subscribing to the VPN service.
Unfortunately, no. These sensors are neither zigbee nor z-wave, so they will only work with the ST-ADT panel.