Mobile games are expected to be a major target for advertisers in the coming years.

Last year, companies spent $87 million on ads in mobile games, according to Juniper Research. But over the next five years, advertisers will focus more heavily on the sector. In fact, the market researcher expects companies to spend as much as $894 million on ads in mobile games in 2015 alone.

However, that doesn't mean that advertising will rule mobile-game revenue. Quite the contrary, Juniper Research believes that fees developers charge consumers to download a game to their smartphones or to buy virtual goods in-game "will still be 10 times higher."

In November, Juniper released a report that predicts total mobile-game revenue will top $11 billion by 2015.

That's probably good news for Angry Birds maker Rovio. Aside from offering one of the most popular mobile games in the world--the title has more than 50 million users playing a cumulative 200 million minutes per day--Rovio is also planning to launch a new in-app payment system.

Dubbed Bad Piggy Bank, the service is designed to make it easier for consumers to buy content in-game. Rather than input a credit card or bank information, Rovio's service will charge consumers on their mobile phone bill, creating a "one-touch payment" system.

In order to implement Bad Piggy Bank, developers need to ink a deal with Rovio. The company didn't divulge details regarding its revenue-sharing agreement with developers but said at the time that it would be "much, much better for developers than current app store models." Bad Piggy Bank is scheduled to launch later this year.