I have recently started writing a monthly article for  the  Locals Only section at Search Engine Land. My first article addresses Google’s  role in the area of voice activated  directory assistance.

Directory assistance with voice recognition and category listings has the ability to permeate the mobile user market place in the near term and could impact local search as much as Google’s Local Onebox. This technology requires no change in user behavior or user hardware and it really works without the advent of more advanced products.
Greg Sterling has reported extensively in this area and has a recent report on an upgrade to Jingles  1-800-Free-411.