I'd just enjoy the trick for what it is - if you dig for an answer you'll just spoil it.
If you're insistent you want to know how it's done then pay attention to what the guy says in the video:
1. Use an OLD cell phone.
2. Use brand new batteries (notice he has to change two of his)
3. Use a CD as suggested NOT a DVD
4. You can use any SILVER coin, but makes sure it is no bigger than a dime.
Have fun
