Nielsen continues to build its portfolio of tracking tools for mobile media.

Since we last reported on Nielsen, they've now purchased Telephia, a private firm that is one of the most respected sources of data about cellphone use, according to the New York Times - tracking consumers' phone calling, mobile Web surfing, video viewership, and so on.

"We follow content wherever it goes across all platforms, and this is a really significant step forward in measuring content across mobile platforms," said Susan D. Whiting, executive vice president of Nielsen, in the article.

Other updates noted in the story: "Nielsen created a new service called Nielsen Wireless last October that has been developing tools to track cellphone use. This month, it announced its first mobile product, Mobile Vector, which will begin releasing information next month about cellphone users. The data will be linked to information from the families in Nielsen's national People Meter television panel."

These tools will continue to build confidence in mobile media, and will give advertisers and content developers a solid point of reference, something that's sorely lacking today.

Nielsen Adds to Cellphone Tracking