Also,
in theory you could use WPE Pro, which is a packet editor, to stop the packet saying that you are typing the message being reached to the messenger servers, which means, that the other user won't see that you are typing a message...
But as i said, in theory...
Gonna test this now...
Or, if I wont edit this post soon with information, it means that I will have probably gone for sleep, and that I would reply after school tommorow...
Edit: Did some research on it ... it seems to be possible, but for some reason, just as Cookie said, you can't see when the other is typing a message
I will do more investigation tommorow...
If someone's intrested, download wpe pro (search google for it) and try making a filter yourself ... (again, search google for a tutorial...)