In reality there isn't need for an secure chat in Skype unlike others, special MS Messenger where is a real need for that! Skype is using Peer to Peer and who would capture packages "on the move" couldn't do anything with them, that would be fragments only which didn't making any sense without the remaining packages. For to get the chat data, is possible only from you computer and not from Skype!
I remember reading articles criticising m$ for changing the protocol, once they bought Skype, in order to satisfy the US authorities, so it possible to snoop on one's conversations... Therefore, this looks interesting... But it's not freeware?