Today, Microsoft Corporation (NASDAQ: MSFT) has inked a deal with San Francisco’s Ingenio Inc. to add pay-per-call ads on Windows Live Search accessed by mobile devices. When searching Windows Live Search on mobile phones, Ingenio will place an ad above the results. These ads will be tailored towards the audience using the phones.

People that use Windows Live Search to find a restaurant or bar in New York City would see an ad for other New York related businesses. When users click on the phone number for the business on the ad, the phone would prepare to dial the business.

Ingenio would charge advertisers for every phone that dials their business from the ad. The price for the phone call is set at a price that is determined by online auctions. Microsoft and Ingenio are more than likely to share the revenue generated from the ad profits.

Ingenio also had ads placed with AOL Time Warner Inc’s (NYSE: TWX) main search engine along with AOL’s mobile search and mobile yellow-pages. Go2 Directory Systems also utilizes Ingenio’s ad placements as well.

Yahoo! Inc. (NASDAQ: YHOO) also announced today that they will go mobile with their ads in the U.S. and the U.K. Google Inc. (NASDAQ: GOOG) also will be soon joining in mobile ads.

So far Microsoft has been the search engine leader that has already deployed mobile ads. Darcie de Freitas, a mobile search product manager for MSN stated “It’s early days for everyone clearly, but this is a big focus for us and an area we’re looking to lead the market in.” The opportunities that are to be gained from mobile advertisement is incredible. It is definetely a market where billions could be made.