Democratic presidential candidate Barack Obama's text message announcing his vice presidential candidate reached 2.9 million subscribers over the weekend, according to Nielsen Mobile.

Users who registered their cell phone numbers or e-mail addresses were going to be the first to know who Obama chose to be his running mate, the campaign said earlier this month. While a cable news network was the first to break the story that Joe Biden was the pick, Nielsen still deems the effort a success.

"While much has been said of the timing and the scoop by news outlets, Obama's VP text message still ranks as one of the most important text messages even sent and one of the most successful brand engagements using mobile media," said Nic Covey, director of insights at Nielsen Mobile, in a statement.

Nielsen determined how many subscribers received the text by monitoring the short-code marketing from an opt-in panel that reports the billing activity of 40,000 U.S. wireless subscribers.

"The value of the message goes far beyond the 26 words and 2.9 million recipients," said Covey. "Here, Obama branded himself as cutting edge, inflated the already enormous press attention paid to his VP pick, and further established a list of supporters' most coveted form of contact: their cell phone numbers."

These phone numbers could potentially be used to fund-raise as well as serve as a cost-effective voting reminder. According to a 2006 study, SMS reminders helped increase turnout among new voters by four to five percent. Additionally, it cost only $1.56 per vote, compared to more than $20 per vote for door-to-door canvassing or phone banking efforts.

The success of this text message campaign could draw the interest of advertisers, as Nielsen points out that 116 million U.S. mobile subscribers actively use SMS, making it "a new mass medium for marketing efforts."