Want to cash in? Invent a phone applications

People looking to cash in on the next gold rush should consider developing applications — or apps — for the new generation of smart mobile phones, according to a forecast released Tuesday by the Yankee Group.

Consumers will spend more than $4.2 billion on apps in 2013, up from $343 million this year, the research firm says, as smartphones become ubiquitous and app prices rise.

The average smartphone owner "downloads about 20 apps per year," says Carl Howe, director of consumer research. "It's a bigger market than a lot of people have been thinking."

Half of newspaper and magazine publishers say that smartphones will become a vital distribution channel in three years, the Audit Bureau of Circulations reports. Only 42% are as upbeat about e-book readers.

Gamemakers also like sales trends for iPhones, aapl BlackBerrys rimm and phones based on Google's goog Android operating system.

Yankee's forecast "may be conservative," says Andrew Stein, director of mobile business development for PopCap, which makes casual games.

Entrepreneurs hoping to become the Bill Gates of smartphones should beware, though.

"It's like going to the racetrack," says Gartner Research's Ken Dulaney. "You hear about one person who made $200,000 in two weeks. But for every one of those, there are 150 others who are struggling."

Contributing: Jon Swartz