What is a UDID?
Each iPod Touch or iPhone has a 40-character unique device identifier.
Apple only allows Apple-approved content to run on an iPod Touch or iPhone.
We register your UDID with Apple to allow our application to run.
1. Plug in your iPod / iPhone and click on it in iTunes.

2. In the summary screen on the right, you'll see this.
Click on the Serial Number.

3. A 40-character device identifier will appear.
Go directly to the Edit menu and choose Copy.
You do NOT need to highlight the UDID to copy it.

4. Hit Escape or click the X to get out of this popup.