Unlike, say, Android, Apple is pretty strict in how it polices its online store, outlawing any app that lets people play emulated (read: usually illegal copies of old games) titles on their iOS device. But it can do little to stop this one.
Riley Testut has built a program called GBA4iOS, a Game Boy emulator for Apple's portable devices that lets you install it outside of the App Store without the user having to "jailbreak" their iPhone or iPad.
It does this by using GitHub, a software development platform, and MacBuildServer, a service that turns code into working apps. This combo lets users install an app outside of Apple's App Store, tricking your device into thinking the app is being used for testing.
Once it's on there, if you had a ROM of an old Game Boy game lying around, you'd be able to make like an Android owner and play old Nintendo games on your phone.
Apparently this loophole has been quietly known for a while, and it's only this week, with the popularity of GBA4iOS, that its cover has been blown. It will be interesting to see how Apple reacts, if there's a way for it to react at all.
Play Nintendo Games on iOS -- Courtesy of Programming Loophole [Tech News Daily, via Game Politics]