Step 1: What You Need
1) Old trousers. Did I mention that they aren't wearable any more when they hold your iPhone? Now you know.
2) Scissors. To cut out the pattern.
3a) Needle and thread. Don't use a thin thread - it should be something that doesn't rip easily.
3b) A sewing machine.
4) White chalk or something to draw on the cloth. You can erase white chalk, that's why it's good, but you can also use a simple pen. You won't see the lines any more, anyway.
5) An iPhone or iPod Touch. That your jacket is worth being made.
Step 2: Choosing the Right Part
You will need a rectangular free space of 28cm x 10cm (11" x 3.9"). This does also mean, no pockets or anything in this space. I had to cut away the clip of a pocket, as you can see on the picture.
Cut it out very generously.
Step 3: Copying the Pattern
Step 4: Sewing the Top
1) Make a valley fold on the top line, so that the 'nice' side is on the outside.
2) Sew 2mm (0.1") under the folding line. If you don't know how to sew (You have an iPhone - You don't need to know), the first picture describes it. Make a knot with the thread at the beginning of the line, then sew until the end of the line and make another knot (No, you don't see the line anymore - It's on the inside. Use your imagination.).
Important: The side where you only see a dotted line (On the first reference picture it's the side on the bottom) has to be on the 'nice' side (the outer side).
When you're done, it should look like in the second picture. From the other side (the inner side), it should look like the third picture (At least when you rotate your stuff 90 degrees).
Step 5: Sewing the Sides
Then sew along the remaining two lines. It doesn't matter on which side the dotted and the continuous sewing lines are.
If you want to have a flap like in the intro-picture, you have to sew it in now. Remember that the flap has to be on the inside of the pocket, because it will be turned inside out at the end. So just lay it where the rectangle in the picture is and sew along the line.
When you are done with both lines, you can cut away the rest of the stuff (about 5mm / 2" next to the sewing lines)
Step 6: Finishing
What I also recommend you to do is sewing a few times around the two edges on top to make the edges more stable and give the jacket the look of something expensive. It doesn't look nice when the stuff is tattered at the edges later.
What may also help is a bit of glue over the threads next to the edges. This prevents getting stuck with the volume-switch of the iPhone in the threads.
Step 7: You're Done!
Congratulations, now you are done and your iPhone doesn't have to sleep naked anymore.