You have to use Colloquy. It works on OSX and now on iPhone. First, Download the latest version of Colloquy.

1. Download their Web-Interface plugin.
2. Install the plugin in the directory: ~/Library/Application Support/Colloquy/PlugIns
3. Create a new password that will be used to login from iPhone. Type the following command in Terminal.app with your password at the end:
   defaults write info.colloquy WebInterfacePassword <<yourpasswordhere>>
4. Open or relaunch Colloquy.
5. Visit http://yourip:6667 on your iPhone.
6. Enter the password you created earlier.