> When I land in a new country it is normal for my cell/SMS not to work. But I can hop on some local wifi and get signal messages.
WiFi calling is a standard feature that does exactly what you describe for texts and calls, without using a third-party. I have cell connectivity turned off constantly on my phone and yet receive texts and calls via WiFi.
It is actually an awesome feature for receiving 2FA SMS at my parent's place where there is great internet but poor cell coverage.