I copied ryan97128 exactly on his set up except there was no need for the battery and I am not experienced enough to put in extra LEDs, so no cool blue hue. For how to break into an Ipod Shuffle, there was this instructable from technochicken which was most helpful.
To avoid redundance, I will assume that you will be able to follow ryan97128 on how to set up the circuit board from the controller and have the Ipod taken apart and ready to go.
Total cost for this project was about $40 for me, the only things I needed to buy were a used Ipod shuffle off eBay and a connector cable for it (you won't be able to use the included stand in my design).
Step 1: Materials
Original NES controller
used Ipod Shuffle, must be 2nd or 3rd gen (the more used the cheaper)
Ipod shuffle connector cable, not a stand (see picture)
hot glue gun
20W soldering iron and solder
swiss army knife (any multi-tool will do)
needle nose pliers
Step 2: Prep Ipod
Deftly remove the buttons by sliding a flat edge (like a small knife) underneath them and prying upwards. You are trying to preserve the two sides of the button which are very small circuit lines on either side of the button (see second picture).
Also, fold out the headphone port like it is in the second pic, it will make it easier to fit in the controller
Do not remove the metal covering around the buttons, this will help you not touch stuff.
Make sure the Ipod is switched to On and Shuffle before you remove the casing
Step 3: Prep Controller
-you will need five buttons, i used the d-pad and A-button, so prepare your circuit breaks appropriately
-I didn't pay much attention to neatness like ryan did, but this project wont be as crowded as his so it is not as important
-save the cord, it conveniently has 5 different colored wires that are useful for the next steps
-prepare the circuit tracks to be soldered to wires by removing their protective covering as described in ryans project
Besides the circuits, you don't need to remove much inside this controller, just a few obstacles on the front piece's inside face. I also prepared the cord hole to fit the headphone jack.
Hot glue the unused buttons down, not necessary, but I found this to be convenient.
Step 4: Lets Solder!
To attach them to the Ipod is a little more delicate:
-do not use a really hot soldering iron, I used a 20W and it should be plenty
-do not fry your Ipod by touching things other than the now stripped buttons
I found it easiest if I had a little blob of solder already on my wires, this kept me from getting solder all over a very tiny circuit. Attach one of each color wire to either side of its desired button, I tried to keep continuity with the d-pad for the outer buttons and A being play/pause.
Test each button after soldering.
I found it helpful to work from the bottom up on the Ipod
The second picture is horribly out of focus so I apologize. If you can, try and get the main idea of what I did, its not that different to what ryan did in his.
Step 5: Finish Up and Enjoy!
Test everything before you screw it together.
I glued the apple logo from the bottom of the Ipod sync and recharge stand purely for aesthetically pleasing reasons.