This instructable was inspired by a few different items on the market. Basically it is just a vest with a lot of pockets in it, some of which are not immediately visable. I am assuming that you have basic sewing experience. This is down and dirty sewing, so do not be offended if my seams are showing. :)
Disclaimer: This vest is just for fun. It is made for travelling, and not for smuggling or anything illegal. I am not responsible for what you choose to do with it. Be careful wearing it thru airports. :)
Step 1: To Begin:
I went to my local thrift store and bought a fleece vest that I thought would work for this, and then I went and fell in love with this silver shirt. If you are really trying to be surreptious, I would use a shirt that is the same color as your vest, though. I also made a mistake in buying a shirt that was smaller than my vest, and telling myself it would still work, which was dumb. :) Buy a shirt that is the same size or a little larger as your vest, it will save you work. The less altering you have to do, really, the better. One of the things that people say about these kind of vests is that they are kind of hot to wear. If that is an issue for you, I would suggest a vest (and shirt) made out of lighter breatheable material. However, the polar fleece was really forgiving and hid my extra sewing well, so keep that in mind.
Basically, what you are doing is flipping the shirt inside out and using it as a lining for the vest. I would pick a shirt with long "tails" so you will have deeper pockets.
1. Cut the sleeves off of the shirt, leaving yourself sufficient seam allowance to turn under around the arms. The armholes of the vest and the armholes of the shirt might not match, so keep this in mind as you are putting together your vest. You will probably have to adjust a little.
2. Trim the collar off, right next to the seam, leaving about a 5 inch piece in the back to cover your headphone cord, plus a little for seam allowance. Turn the edge under, and sew. I used fray check on the cut off edge of the collar. If you want to sew snaps or an extra headphone loop or two, inside, go ahead. I would suggest not using velcro, however, or buttons. They might get caught in your hair if it is long.