Most Secure Digital Audio Player?

PaleGreen asks: "What's the most secure portable Digital Audio Player (DAP) in terms of a true 'one-way' file copy mechanism? I want to be sure a curious coworker can't leech my portable's treasures while I'm out to lunch (or even worse, if I lose it). I'm aware of 'iPod backup' solutions that seem to get around Apple's protection. Are the Windows Media 'Plays For Sure' devices more secure in this area? Are there portables that support a hardware password (similar to a BlackBerry, where the unit resets to factory defaults after ten bad password attempts)?"