A plastic screen would have been a complete disaster. Apparently none of you owned an iPod pre-iPhone days. The screens got scratched if you looked at them funny.
I once wanted to try using the backs of iPods as part of a keyless entry system. We all carried iPods anyway, and everyone's iPod had a different scratch pattern on back, so have a system where you hold your iPod back up to a camera and enter a PIN. The scratch pattern tells the system who is requesting entry. If they enter the PIN for that person let 'em in.
