Mobile phones offer plenty more than just voice these days. They can provide news, video clips, local weather and even restaurant recommendations.

Problem is, many customers can't figure out how to access all that information. That's where companies like Google and Yahoo, along with a slew of start-ups such as InfoSpace, JumpTap and Medio, see a big opportunity. These companies are developing tools that allow users to search for content. And they're starting to test search-based advertising to help generate revenue.

"When there were only 10 ring tones and a handful of other sites on the carrier deck it was simple," said Iain Gillott, an analyst with iGillott Research. "But now there's 10,000 ring tones and it's really hard to find what you want. It's like walking into Wal-Mart with only the aisle numbers to guide you to what you want to buy."

As revenue from their voice services continues to decline amid pricing pressure, mobile operators are counting on mobile video, music downloads and other data services to make up the revenue difference. But so far, most of the 190 million wireless subscribers in the United States have not downloaded content onto their phones or surfed the mobile Internet looking for content.

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