Was hoping this was about earthen tunnels and was pleasantly SURPRISED considering the website we are on :)
My thoughts exactly. I’ve been using them for exposing local services to the public internet from my home network. Super convenient for initial proof of concept work…
I use them as cheap-man's VPN. A ssh server on a public IP but a non-obvious port brings you into the network, and port forwarding allows you to connect to relevant endpoints in your remote network via localhost:12345.