Google has updated Chrome 27, it includes conversational voice search. This feature is demonstrated on stage at Google I/O this year that allows you to do voice search.
Conversational search is available in the latest Chrome version 27.0.1453.93, In Google home page you should click the microphone icon in the search bar. It will ask you if you want Google to start listening, then you should not click any longer.
The problem is that Google is not reply to queries, unless you click the mic icon as usual. In a natural way you can continue the “conversation”, and Google will understand that you are talking about the same subject.
So if you ask it “Who is the president of the United States?” it’ll answer Barack Obama, after which you can ask “How tall is he?” and it will understand who you’re talking about.