The company said the investment in JumpTap, which will be able to conduct more than 250m searches a month by the end of 2007, would provide advertisers with better access to consumers.
JumpTap, which was founded in 2004, specialises in the mobile and ad search market, and agreed a deal with Virgin Mobile USA in December to make its search mobile technology easier to use for accessing specific websites.
Mark Read, chief executive officer of WPP Digital, said: "Our clients want to understand how to use mobile devices as an effective channel to reach and communicate with customers.
"JumpTap's business model helps mobile operators gain greater value from mobile search and advertising and its products will help advertisers target more customers effectively."
Dan Olschwang, president and chief executive officer at JumpTap, added: "In essence, our mission is to help advertisers and mobile operators build a thriving marketing ecosystem where people on the go can find exactly what they want."
The acquisition comes as WPP announces that its media holding company GroupM has acquired the entire issued share capital of Dutch digital media and eCRM agency Reddion.
Founded in 1998, Reddion is based in Rotterdam and employees 22 people. Clients include Unilever, KPN, Postbank and FBTO.
Reddion's turnover for the year ended 31 December 2005 was €2.2m, with gross assets at the same date of €3.4m.
WPP said the investment continues WPP's strategy of developing its networks in fast-growing sectors and strengthening its capabilities in digital media.
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