I know that hard-drives have some sort of indellible serial number that uniquely identifies them, WinXP uses it to make sure you don't reinstall your OS on another drive without paying them again.
Do SD Cards and Memory Sticks have a similar "hardware serial number" that could be read? If so, I don't see why protected contents couldn't be locked/encrypted to that SN and thus unreadable anywhere but from that card.
Copy the file? Go ahead but it won't open anywhere but on that SD card. I still think this could work.
