Update: And as expected, the app described below has now been pulled from the App Store. It actually lasted longer than I thought it would.
An iPhone app called Awesome Baby Names has a secret Game Boy Advance emulator built into it, as 9to5Mac has discovered. The emulator is easily unlocked via a simple sequence of taps (depicted below by iPhoneblog.de), but if you do want to unlock it you’d better get it quick because Apple is sure to pull this one quickly.
The process of unlocking the emulator is simple, but getting the ROMs and BIOS where you need them to get it up and running is a little trickier. You’ll need iTools, which lets you access your iPhone’s file directory (without jailbreaking). Once you have that, navigate to Apps in the sidebar for your connected iPhone or iOS devices, then find the “Files>Documents” directory and drop the relevant BIOS and ROM files there.
If you’re interested in emulation, you probably know enough to get you the rest of the way there. If not, there’s a great search engine called Google I can recommend. Apple will surely be removing Awesome Baby Names from the store now that this is out there and public, so act quickly if you’re after some emulation action.