Fingerprint scanner in minecraft

1. Put a comparator behind the item frame
2. use a command block to find the redstone level of the comparator or just a regular old password switch will do
3. Then a simple player testfor command will take it from there

With command blocks you can use this setup:

1. First, use a repeating command block that's always active with the command:

/testfor @a <coordinates of block in front of your "scanner".

You can then have a comparator run out of it and into the second command block.

2. Then a repeating command block which needs redstone:

/testforblock <position of wool block>

Then have a comparator running out of two redstone dust one piece to the left of the first piece and one to the right of the first piece.

3. Last, place a command block at each end of the redstone dust the one two the left which should say:

/setblock <coordinates of were the wool should be> wool <data value of the color you want>

The right one should say:

/setblock <coordinates of the left of the wool> concrete <data value of lime>

and the front one should say

/setblock <the block under the block under the door> redstone_block

Out of the front and right block should be a comparator 2 repeaters set to four tick and another repeater set to 2 ticks for a 1 second delay attached to both of those should be a command_block. The right one should say:

/setblock <where the lime concrete is> concrete <data value for red>

The front one should say:

/setblock <the block under the block under the door air.

For 1, you can either use a /data get entity @e[type=item_frame,limit=1] ItemRotation or a comparator.

For 3, you can simply just use /kill @e [type=item_frame,limit=1] and then /summon ItemFrame <x> <y> <z> {Direction:facingb,Item:{green_stained_glass_pane}} replacing "facing" (leave the letter b as it is) with the way it is facing (0=south, 1=west, 2=north, and 3=east.)

Also, item frames count as entities, not as blocks.