Small and quite useful accessory. One of the main shortcomings of the Canon DSLR is the fixed position of the LCD screen - viewing the screen during focusing and composing the shot can be quite awkward, in particular when the camera is attached on a small mount on short tripod (like my P2Z) and the object is located near zenith.
In order to make the viewing a bit easier, I have devised a small plywood part which attached to the camera tripod socket with 1/4x20 screw and supports push-fitted small tiltable mirror - a second hand component from a microscope (used to adjust illumination of the viewed field). The added benefit is that one of the mirror surfaces is concave and therefore provides slightly magnified view, which also helps in the critical focusing. Mirror can be tilted and rotated to bring right portion of the image into view - unfortunately it is too small to cover full display.
The mirror attachment is usable only with my 200mm lens, where the camera is attached by a separate L bracket.
Quite usable, took probably an hour to manufacture. One caveat - while in the field, one need to cover it between uses, as it quickly gets covered with dew or frost.