I had a similar idea... You create like a firewall type application, where for example you could do an ssh connection to this box from the web, and it will then do the telnet for you from there on. Of course this idea requires some programming, or you could just ssh into a Linux box over the web, and then telnet from there ;-)

One option would be to map a port (I think the command is redir on Linux), which will allow you to connect to a gateway box, which will then redirect you automatically to the other box.