As a user of Google Voice I can see how a standard voice over bluetooth system would not be sufficient to allow a user to manipulate the features of Google Voice verbally.
I am sure that when "Voice Control" does appear...it will allow a level of control of the Google Voice application that will change the way we use our phones.
"Bob is calling"
"tell him the number is disconnected"
"Patti is calling"
"Ill take it"
"the IRS is calling"
"Ill take it, please record" (send me a transcript via text )
Your mother is calling.....