If you have a Hogwarts event to go to, but don’t feel like dressing up as Harry or Hermione, you could instead go as Mad-Eye Moody, wearing a prop made via dad-hacker “daronjay’s” excellent instructions. The device uses a micro hobby servo to move the eye left and right (at a slight angle to add to the craziness), and is controlled by an Adafruit Trinket, both hidden inside of the eye glass/patch.
To make the wearable eyepiece, daronjay cleverly modified a brass colored bottle cap to form the front of the assembly, along with several slotted screws to enhance the effect. The cap of a deodorant container was then modified to complete the design, adding some needed height in which to hide the servo. The servo — which itself had to be slightly modified to fit — and Trinket were then mounted inside the enclosure, moving an eyeball that he found online around. You can see it in action below!
If you’d like to go even further, the design is based on Adafruit’s 3D-Printed Bionic Eye, which is somewhat larger, but uses two servos to move the eye up and down as well as left and right!