Regarding Tox as Skype replacement:
There are already GTK/Qt/QML frontends, but the question is - do we need another separate app for this protocol? Of course we don't.

Tox Telepathy plugin hasn't been made yet, but there's already a Pidgin's libpurple plugin available. We already have telepathy-haze in the repos, so using this plugin in the integrated messaging app should be quite easy. We just need to compile Tox and the libpurple plugin.

PS: Corrent me if I'm wrong - this is the first time I hear about Tox.