I am using a 3" 4:3 "Digifinder" display-viewfinder on my Panasonic GH-1 but found that:
a) The way to mount it with a rubber band is ****
b) I can't see the edges of the screen where battery-level and other important information is shown
This adapter fits perfectly onto the screen of a GH-1, GH-2, FZ100, ... camera and can be attached and detached without any rubber band chaos.
It allows to mount the digifinder at a longer distance and thus see more of the display.
There is even enough room in the visible area to drill some holes and insert micro-LEDs as indicators for e.g. audio-level warnings or to have some feedback that the audio recorder is actually recording at the moment.
* design files on Thingiverse
* photo album