thinks of nimbuzz, did Google and FB work yogether there?
Something like nimbuzz would work if the respective data owner opens up access to their service. AFAIK, for numbuzz(IM), both Gtalk and FB allows access to their respective chat platforms(via XMPP).
I cant say I know the specifics of the FB graph API, but if that is open & G+ is open, then the developer would authenticate, search and retrieve onto his/her application. As long as they are opened up. All things holding, seems quite possible. I havent heard of an official API for Whatsapp though. As for the others, it would be a matter of what they allow you to do