By gMail/gTalk, answer is simply, -> NO application is XMPP Voice & Video compatible.
gTALK use XMPP protocol. Voice&Video over gTalk => (XMPP-Jingle).
You pay 500USD for a tablet that cant MAKE A SIMPLE CHAT VOICE CALL.
Who use XMPP?
gMail/gTalk, Facebook, Ovi Nokia, Jabber, NEC, and many many many companies.
To be sincerious, my Nokia n95 with Talkonaut (xmpp compatible client), I can make VOICE & VIDEO CALL. With a mobile of pennies instead of 500USD.
That's a SHAME.
SHAME ON YOU GOOGLE.
We are still waiting an XMPP Client with Voice & Video.