Kyuran ported his Nintendo DS Amstrad CPC emulator CrocoDS to the Apple iOS devices. It is heavily based on WinCPC by Ludovic Deplanque. Most modifications to make it run on the Nintendo DS were already made about 6 years ago. The source code is available on GitHub.
To use it on your Apple device, you have to open the .xcode file on your iPhone / iPad. The disk images (.dsk files) have to be send via iTunes.