Heyzap, a platform that lets gamers share and discover new apps, has brought its game check-in app to the iOS platform after seeing some initial traction on Android.

The app basically detects what games a user has been playing, lets them check into their favorite apps and share them with friends on Facebook and Twitter. Heyzap launched an Android version of this back in March and it’s seen between 500,000 and 1 million installs, according to Android Market’s statistics.

It’s not the first time we’ve seen a check-in concept for games. IGN released a check-in app for video games called Dominate last month. Then there are several standalone discovery apps (which don’t necessarily involve check-ins) like Appsfire, which just raised $3.6 million, Zwapp, Chomp and Apptitude. Plus, many of the mobile gaming networks like OpenFeint, Scoreloop, ngmoco:) and PapayaMobile have similar broadcasting abilities, which allow friends to share their favorite games and achievements.

Developers are certainly looking for cheaper and more effective ways to acquire users, but we’ve yet to see a killer third-party discovery solution, both in terms of a product and as a business. If consumers can’t discover the discovery app, it’s hard for these standalone solutions to drive a meaningful number of new users to any developer.

On top of that, because Apple retains control over payment processing on iOS, even if an app like Heyzap acquired millions of users, it might be difficult for them to earn revenue through their gaming network. While early to the space, OpenFeint had similar issues. When it was bought by GREE for $104 million, it had just $282,500 in revenues and posted a net loss of $6.6 million last year.

There may be more revenue opportunities for a third-party mobile gaming network on Android because of its open nature and the fact that there are several app stores. DCM-backed PapayaMobile is making a bet on this with its Android mobile gaming network. But, of course, Android is still far away from monetizing at the level that iOS does for developers — and the two may never reach parity on a per user basis.

Heyzap, which started with Flash gaming as a YCombinator-incubated startup, is moving with the rest of the developer community toward mobile devices. The company has raised $3.65 million from Union Square Ventures and other angel investors including Naval Ravikant, Chris Dixon and Joshua Schachter.