1. Put a blank white photo on your iPod and view it. Take a close-up shot and you've got your iPod-screen texture.
2. Make your fake screen in Photoshop--you could use pieces extracted by alterPod etc. (apps used to re-skin the iPod UI).
3. Layer your fake over the white-screen photo in Photoshop. Use Multiply mode to let the screen texture come through perfectly.
4. Free Transform and drag the corners into perspective.
5. Blur as needed to match the photo, and Adjust Curves to reduce the quality like an LCD.
7. Feel the need for reflections/glare? Take them from a similar photo of the iPod turned off. Composite that screen on top with a mode of Screen. Set curves on the layer to get a true black if you need to avoid brighting the whole thing.
8. Need to have focus or brightness or color/sat vary across the screen? Make a slightly different version, and composite that over the top. A soft layer mask with a big brush (or even a gradient) will let you paint in a gradual shift of focus or lighting.
But as I said, these fakes were made by a less fun but much simpler method