Octoprint has always been one of the best upgrades for a 3D printer, which is why I made both a mounting plate for the Raspberry Pi 1B+, 2B, 3B, and 3B+ and a camera mount for monitoring prints on the Prusa I3 MK3.
The mounting plate that I have created allows for you to directly mount the Raspberry Pi to the Enisy Rambo case on the Prusa I3 MK3. Although it has been designed to not run into the stepper motor, I have also included the STL for a flipped X motor mount if the Raspberry Pi mounting does get in the way at all.
The instructions and bill of materials for mounting the Raspberry Pi can by found here:
The camera mount that I made consists of small segments that link together. There are three versions available: one that uses M3 nuts and bolts, another that uses M4, and a final that uses M5. There is also a respective mounting part that attaches to the X stepper motor for each size (whether or not it is flipped), and a rotation segment that allows you to rotate the end point where the camera would mount. I did not create any specific camera mounts; however, I did use GoPro-sized joints, so any camera mount compatible with GoPro products will work. This camera mounting system for the Prusa I3 MK3 can be used as more of a starting point for mounting your camera.
Note: I do not have a Prusa MK3 to show what is would look like in real life, so I have created various renders that depict how the different parts can be used.