Using a loophole in Apple’s app installation systems, this emulator can easily be installed on any iOS device, for free. There is a slight (but seemingly easily) trick you must do to your iPhone settings. After you perform the hack, you can download the app directly from the GBA4iOS website.
The emulator with full support for Game Boy Advance, Game Boy Color, and Game Boy itself, plus accelerated speed and Dropbox syncing for saves between multiple devices.
We’re not sure if this conforms to the App Store’s terms of service (so watch out) but if you’re missing your long-lost Game Boy this may be fun to play with!