Yahoo (NSDQ: YHOO) has launched voice-enabled OneSearch for its iPhone app, which will let users conduct a search by simply speaking. The service also lets people customize the My Interests tab by clicking on “add anything”, speaking the topic they’re interested in, and selecting the relevant content to add. The voice service was already available on BlackBerry, Nokia (NYSE: NOK) and Windows Mobile handsets (Yahoo expanded to the latest BlackBerry devices today). Yahoo has also launched a shortcut for oneSearch on Windows Mobile in 21 countries.