The basic idea goes like this: install one LED on each Piano key and turn each LED on/off to show which key to press down for each note in a song. The implementation involves an Android Phone, IOIO Board, and an LED module. I thought I was the only one who came up with the idea but it turns out there was a startup company based on this idea. Booohh
Android cannot control shift registers by directly sending out bits. Intermidiary is needed so the system like IOIO board is needed. The project is nearly done so I will post a youtube video of me playing piano with the LED module. Standard music media format MIDI is parsed within anroid phone to send bits to the shift registers. This can be done with external java library found by googling.
This is the photo showing the IOIO board+74HC595 Shift Registers+ Arduino Board. Why do I need Arduino board? Well I forgot to buy power supply so now Arduino's 5V Pin/Ground Pin is being used to power IOIO board. LOL. Above all, JAVA is needed to program Android and even for driving IOIO board.
(Edited 10/9/13: Comment here if you have questions about the setup.)