This is not the first time that Android has been ported to an iOS device. Bootlace, by iDroidProject ported the Android OS to the iPhone 2G and 3G. Now, the same guys have are bringing OpeniBoot which would support new generations of iOS device like iPad, iPhone 3GS, iPhone 4 and the second generation iPod Touch.
OpeniBoot is an open source implementation of iBoot bootloader for iOS device, allowing them to dual-boot on Linux based OS, like Android. The guys at iDroidProject have released a video of Android running on iPad. OpeniBoot for newer iOS devices is not available for now, but the video suggests that it would soon be.