Here is a list of some really great apps for producing Chiptune music. Let us know if you can think of some more!
Nanoloop for iPhone combines sequencer, synthesizer and sampler in one package. It provides all functions for creating electronic music from scratch. http://ipadproducers.com/gameboy-nanoloop-for-iphone/
MicroSynth is exactly that, a tiny synth based on a wonderful Micro Computer which is now on the verge of being 30 years old! All of the sounds you hear are actual samples taken from a real Micro and all of the sounds were programmed by Pixelh8. I hope you you enjoy making music with this MicroSynth. http://ipadproducers.com/free-bbc-micro-computer-synth-app-for-iphone/
NESynth By newforestar co,.ltd NESynth is a synthesizer that simulated 8 bit sound of video games in the 80′s. http://ipadproducers.com/8-bit-chiptune-for-iphone/
8Bit Studio – the only circuit bent 8bit SID synth for your iphone! Customize your patterns using the built in step sequencer or play live on the retractable keyboard then bend and distort the sound using the touch contacts! http://ipadproducers.com/8-bit-chiptune-studio-for-iphone/