Here's an idea I've had floating around in my head for a while for a higher security lock.
use a key that has laser drilled holes in it in a specific pattern. The tumbler will have sealed acrylic windows in either side for the light source to pass through. use an array of ir diodes on one side, and a ccd array on the other. if the pattern in the key is correct, the ccd sensor matches what it sees in the ir image pattern against one stored in memoty and then operates the unlocking mechanism. This would allow for physically separation of the key and tumblr from the locking bar, and you could seal the keyway internally so that nothing could be pushed through. even if the ccd array were fairly coarse density, you could do a laser drilled array on a key face that was 5 rows high by 25 columns long down the length of the key. It essentially makes it a binary combination lock that you cant physically manipulate.
Could this possibly be an unpickable lock?