Google Voice + Gmail, you can:

* set GV to forward txts to GM, replying to the email will reply to the txt

* have transcribed voicemails emailed to you with a link to play the original in the email

* use the "Call phone" button under chat to make outgoing calls via the web for free (for now)

I think that's what he meant, at least. Only one of those things (the last) isn't available outside of Gmail itself.