The Gadget Hacks team has built a simple one-tap mod that allows you to dual-boot Android on your iPhone right from your browser by utilizing a mobile-webkit buffer overflow, and taking advantage of the fact that both Android and iPhone CPUs use the same ARM instruction set. Using the same techniques, we've also built a way to dual-boot iOS from Android. Visit AndroidHacks.com from your Android phone for that mod.
iPhone 4s, iPhone 5, iPhone 5s, iPhone 6, or iPhone 6 Plus (iPad support coming soon)
iOS 7 or iOS 8
1 GB of free storage space
No jailbreak required
100% reversible (as easy as uninstalling an app)
None of your existing data will be touched (no need to reinstall apps or contacts)