Look for Metal Detector. Run that, lay your phone on a table, and pass objects over it. Metal ones will make the phone vibrate. Non-metal won't. Doesn't work with aluminum, but most other metals work.
I did that last weekend with some iFriends and they were quite shocked and impressed that my phone can detect metal. Seriously, try it, it works!
Excellent, got it setup for DL. Thanks for the suggestion!