Heyzap, a startup with a mobile social gaming network, is announcing today a way for mobile game developers to reach its network of millions of users.

The cost per install (CPI) program provides mobile game developers with a quick and easy way to acquire new users. Heyzap thus helps attack the major problem that results when the presence of too many similar apps make it easy to get lost in the shuffle.

San Francisco-based Heyzap has created a free check-in app where users log in and say which game they’re playing on both Android and iOS (Apple’s iPad, iPod Touch, and iPhone platform). Friends can use that app to discover new games and join their friends in multiplayer play.

The app has millions of users now, so Heyzap has begun monetizing it. Heyzap is doing so by promoting games as “the game of the day” to its users. Developers who advertise their releases in this way will pay Heyzap and get thousands of new users who download and install “the game of the day.”

Participating developers include TinyCo, Pocket Gems, Com2Us, Pixonic, and Gameloft. Traditionally, mobile game developers advertise their releases on incentivized download networks, which reward users with in-game currency for downloading promoted titles or banner ads. But these methods rarely attract loyal users. External rewards motivate players when they download a promoted game, and sometimes they’ll uninstall the app immediately after collecting their reward.

Heyzap hopes to attract mobile developers who are moving away from incentivized downloads. Heyzap’s nonincentivized CPI promotion system is designed to help developers reach actual gamers on Android and iOS. Heyzap’s users may download “the game of the day,” and if they do, their friends will see that they have done so and may do the same.

Heyzap has partnerships with 1,300 mobile game developers. It has raised $6 million from Union Square Ventures, Chris Dixon, and Naval Ravikant. It was founded by Jude Gomila and Immad Akhund.