I'm excited about Sandstorm eventually helping people tackle issues like port forwarding. There's enough to do that it's not something I'm personally prioritizing, but it would definitely be very interesting. I can imagine the initial version of this feature working using UPnP for example, for routers that support it.
Thanks for taking an interest in Sandstorm!
As for ngrok-style tunneling, that's something I'm less interested in hosting/maintaining as part of the Sandcats toolkit for Sandstorm self-hosters. I'd be happy to see Sandstorm grow the ability to integrate with services that offer something ngrok-like, though.
Somewhat hilariously, a Tor hidden service is easy to set up and has built-in NAT traversal, if I understand things correctly, so maybe one day we'll see a "Run your Sandstorm server as a Tor hidden service" feature purely for the connectivity conveniences.