White label mobile search provider JumpTap - whose mobile operator customers include AllTel - has become the latest to add pay-per-call to its repertoire, running the ads on its service through a deal with Ingenio. (The press release hasn’t been posted yet.) The partnership will feature Ingenio pay-per-call listings within JumpTap’s mobile search system, and marks the fourth big-name win for Ingenio, a provider of pay-per-call advertising. Ingenio’s other mobile partners are AOL Mobile, Go2 and Microsoft’s Windows Live Mobile. (Pay-per-call allows local advertisers to bid to receive a call from the searcher, deciding how much they are willing to pay for calls received. The pay-per-call advertiser only pays when a consumer initiates a call to the business from their mobile phone, so results are real and measurable.)

So, why the sharp focus on pay-per-call? In a nutshell, this approach to mobile advertising, which essentially targets users when they’re already in buying mode, can literally pay dividends for mobile content companies and advertisers. The proof is in the bids, which industry insiders tell me can range between £2 - £70 ($4 and $136).  On Ingenio’s system, the average advertiser bid per call is currently between $8 -$10. Other stats that make a convincing case for pay-per-call come from the Kelsey Group. It predicts this emerging market – driven by the increasing popularity of local mobile search – could be as large as $4 billion by 2010, or nearly the same size of the Internet search market today.

The business model also has its share of pros, according to Dan Olschwang, JumpTap CEO. In an interview with ClickZ, he said “mobile search represents the ’last mile’ for advertisers seeking to reach consumers at the point of decision, and pay-per-call connects the two when user intent is at its highest.” Marc Barach, Ingenio CMO, is equally bullish on the fit between the two. “Consumers are starting to be mobile information consumers. As a result, we’re seeing hardware and services providers cluster around that need, providing better ways for consumers to use their devices to get local services and information….We believe pay-per-call as a business model will be the primary monetization model for mobile search, bringing more advertisers to that environment and serving useful content to consumers.”

Pay-per-call, the voice equivalent of pay-per-click, is a low-risk, high-reward way to monetize local search – but will it help sell mobile content? Hard to say. However the traction pay-per-call is gaining among mobile search companies (including the likes of UpSnap, which has developed a pay-per-call scheme that turns a user’s query into a response that links users with a merchant via a free VOIP connection, paid for by the merchant) indicates it will be an important and unavoidable component of mobile search monetization schemes moving forward.