alt Hacker NewsTailscale running in subnet router mode on a GL.iNet router comes close. You can setup Tailscale through the GL.iNet GUI but to have it also route traffic for everything over to your Tailnet you need to flip one setting via an ssh command.
Not as convenient as this travel router sounds though, but comes close-ish for techies. (wish it didn't require that tweak via SSH. Maybe it'll be added)
Something something dropbox is simple :) https://news.ycombinator.com/item?id=9224
I wish Eero offered this feature. I bring three eeros to Airbnb’s to replace their crappy WiFi with my same SID, but it would be nice if it connected back through the home internet.