It depends on how you build the RAID.
A hardware RAID card with SAS drives might blink a LED on a failed drive. Might since this varies with the hardware used. E.g. HP RAID cards and SAS drives in HP caddies flash a green LED for 'failure predicted' and turn on an orange LED fro 'failed'.
In the case of software RAID and the right drivers you might be able to do the same.
However you can always use these two methods without special hardware.
1) Label the drives with a name
Do not mount disk 1, or add /dev/sda and /dev/sdb to a mirror. Instead of using the disk descriptions give them a label which is stored on the drive
tune2fs -L BOOTDISK /dev/sda1 Mark SDA1 with the label BOOTDISK
e2label /dev/sda2 BOOTDISK Either command should work.
e2label /dev/sda1 Read the label to check if it worked
And in /etc/fstab, replace
/dev/sda1 /boot ext2 defaults 1 2
LABEL=BOOTDISK /boot ext2 defaults 1 2
2) use the UUID label on the the drives
This is sort of a serial number for the drive.
You can check these with the command
Print these labels and put them on the drives.
Then create the RAID device based on these labels instead of physical disk order.
See also this post on redhat.com with more details
Lastly, you mentioned unscrewing drives as an option. I suggest just pulling one of its connectors sicne that is easier to do.