Hi.
If you want the exact same functionality of fastssh.com then you can deploy that on any Unix Flavor. The only prerequisite is to have OpenSSH (sshd) protocol 2, which by the way, is hihlgly likely to be within the core installation of most distros, even in "minimal" packaging.
The next step is to disable shells. Yoy may do this changing the default profile so whenever you add a user, it gets created without shell such as /bin/false or you may achieve the same thing as per user basis editing last column of /etc/passwd.
The final step is to create automation and a front end that triggers it. Maybe you want to verify each request prior to accept it and give them a tunnel.
I think a very important aspect is to take into account is the bandwidth, due to the fact that all the traffic that the user fetches, will go through your infrastructure.
