I am pretty sure that you can do this with just an SSH tunnel:

1. from your local machine: ssh -R 9000:localhost:9000 xdebug-machine
2. configure xdebug on the xdebug-machine as "remote_host=localhost".
3. configure your IDE on your local machine to listen to port 9000 (which should be the default).

If you have remote_host=localhost - and have xdebug setup to interact with the ide if you load the page via browser, it won't do that unless you have the actual ip. The tunnel might reach the client, but the session won't get fired off because it's looking for localhost. Inverse, if you have remote_host=<my_ip>, it attmpts to start the debugging session from the browser, but won't connect to the client because it's not tunneled.

best way to explain it would be variables like:
listen_host - listen for a particular ip e.g. 10.0.0.5
and
return_host - which could be set to localhost (for the port 9000 communication)

What you say is not true; I just tested this with the following setup:

1. local machine has Komodo running, and listening for debug connections on port 9000
2. ssh -R 9000:localhost:9000 xdebug.org

3. in that opened shell:

   export XDEBUG_CONFIG="idekey=dr"

   echo '<?php function foo() { $a = 52; } foo(); echo strlen( "basdfadsf" );?>' > test8234234.php

   php test8234234.php

And I get this connection popping up in Komodo. If there is anything that prevents this from working, it's your IDE.