Duplicate terminal for presentations

If are giving a presentation and you want to see what are you writing, without duplicate the screen, you can open two terminal windows and duplicate the input and output of one to the other:

1- Open two terminal windows

2- In one of the terminals run: $ screen -S foo

3- In the other one run: $ screen -x foo

4- And that's it!!! All what you typing in one of the terminal window automatically is shown in the second terminal window.