In the surest sign yet of the importance of mobile media, RCR Wireless News' Kelly Hill reports that starting next month, The Nielsen Co. will measure mobile phone media access through a new service called Nielsen Wireless, which will do for cell phones what the company's TV Ratings do for television.

"Nielsen Wireless' first product, Mobile vector, will rely on information gleaned from Nielsen's National People Meter TV sample," Hill writes. "The company said that the service is designed to identify how subscribers of different carriers consume different types of media in the home; help carriers develop more efficient advertising; give mobile content producers information on which mobile content distributor will best help them extend their brands; and help companies establish competitive positioning and differentiation."

"The value of an entertainment medium is directly proportional to how well it is measured," says Nielsen vice president Jeff Hermann. "Reliable and accurate measurement of mobile consumers will enable advertisers to properly evaluate the mobile marketing opportunity."

More here from AdWeek ... more here from the AP ... more here from Reuters ... and the press release is here.