`ssh email@example.com -R [remoteport]:localhost:[localport]`
Where 'yourserver.com' is a server you own, such that accessing 'http://yourserver.com:[remoteport]' tunnels to 'http://localhost:[localport]'.
Giving you full benefit of doubt that you just haven't fully explored ngrok, instead of just listing the features here myself, I'll just urge you to check it out in more detail.
It's awesome little tool, and the author has always been enthusiastically responsive through #ngrok on freenode.
The other benefit is that ngrok provides a nice web interface so you can watch and inspect web requests as they go by.
You can host with companies a lot smaller than Google or Amazon. Let someone else carry the pager, you know?
How are they supporting so many IPv4 tunnels? Presumably they don't have the IPv4 space to assign standard ports to them. HTTP is easy but they say they let you "expose any networked service".
Why are folks only worried about the closed source client, which likely does nothing interesting, when all the magic must be at the backend?
Also good to quickly let friends try your local server.