He means instant messenger. This idea has been tackled before and I do like this suggestion but it is easy to get past this. Just add the person on AIM (or talk to them and make an agreement taht you will both get AIM).
You can always make a 2nd AIM acount if you are not comfortable sharing your main AIM username. I do think it would be cool to have instant messenger on ArmorGames but I am not too sure if this will ever happen.