[toomuchtodo]

You're asking for a magic genie content router that does not exist. It does not exist because its a hard problem. Not only would you need to interoperate with open standards, you'd have to attempt to integrate with unwilling participants (Facebook, Google Hangouts). Are you prepared for that level of pain?

[Ntrails]

You also have to consider that facebook already do this. They tried to wrap up email, messages and an SMS replacement on your phone into a single package where they own the whole thing.

I look at iMessage and I think it works pretty perfectly, SMS when no internet or to a non apple user, iMessage whenever possible. What I want is for whatsapp (and I suppose facebook and plausibly email) to do the same all in my single messenger application.

But. Ignoring the need to get the tech owners to consent to this new "trillian", I'd also have to trust the app itself. Good luck making money on that.