Yahoo! Inc. has acquired Qwiki Inc., a mobile tool for creating videos on Apple iPhones, as Chief Executive Officer Marissa Mayer seeks to add technology and engineers in the area of mobile software.

Earlier this week, the company acquired Bignoggins Productions, a mobile application for managing fantasy sports teams.

Qwiki’s app will continue to be supported and its employees will move to Yahoo’s New York offices, the Sunnyvale, California-based company said today in a statement. Yahoo paid as much as $50 million for the startup, technology blog AllThingsD reported. Terms of the deal weren’t disclosed.

Mayer has emphasized mobile apps in her bid to win users and advertisers back from Google Inc. and Facebook Inc. Improvements to Flickr, its photo application for smartphones, have helped Yahoo top 300 million monthly mobile users, up from just 200 million at the end of last year.

Qwiki’s software lets users create video slideshows from the photos and movies stored on their iPhones, and embellish the clips with music and graphical transitions.

The technology may be used to enable video creation on other Yahoo sites, Mike Kerns, Yahoo’s vice president of social and personalization, said in an interview.

“We’re clearly interested in using acquisitions as a means to bolster talent, bolster technology and improve our product suite,” Kerns said.

Shopping Spree

Yahoo has acquired at least 15 companies since Mayer was hired as CEO a year ago, including the $1.1 billion purchase of blogging platform Tumblr Inc. She has also snapped up mobile app makers Stamped Inc. and Jybe Inc., as well as Summly, the news-reading application created by teenager Nick D’Aloisio.

The deal represents a coup for Bignoggins founder Jerry Shen. He quit his job as a software engineer shortly after starting Bignoggins in San Jose, Calif., three years ago and proceeded to develop a series of mobile apps for players in fantasy sports leagues.

Bignoggins apps such as “Fantasy Monster” and “Draft Monster” proved to be popular enough to convince fantasy sports players to pay for the service, helping Shen to finance a trip around the world that his wife, Adrienne, blogged about at http://www.shenventure.com/ .

Shen, 30, is joining Yahoo’s mobile engineering team at the company’s Sunnyvale, Calif., headquarters. He is the only Bignoggins employee joining Yahoo.

Yahoo isn’t going to keep distributing Bignoggins apps, but will blend some of the underlying technology into its own services for playing in fantasy sports leagues.