UPDATE 15th March 2013: I have newer better version of this now in another Instructable:
Believe it or not the real purpose of this project was not to play at being a Borg.
I needed to make some form of wearable head up display that also allowed me to work simultaneously, i.e. see what I was doing at the same time, to test the feasibility of a concept for a research idea I have had. I needed to for example be able to remotely watch a video screen with data on it and also later may want to view protocols, checklists etc on this "head up" display.
My interest in this is because I think wearable displays will be a valuable tool in hospital medicine, especially in anesthesiology.
The proper name for this is a monocular HMD (Head Mounted Display).
A number of video-glasses already exist for watching DVD's for example and these generate an image for each eye. The downside is that you cannot see your surroundings while wearing them.
So-called monocular (one eye) displays do exist but can be very expensive. I already had an old pair of Olympus Eye-Trek(TM) video glasses, which are (relatively) inexpensive and decided to hack them and embed one of the display units into a pair of workmans safety glasses.
Then, having made this display work, I used the innards of a wireless security camera / receiver combination to make the system work wirelessly and finally packaged all the circuits with appropriate batteries into a just-about-pocket-sized container.
This project might also interest the "wearable computer" fraternity. You could also attach an infra red camera to it to give yourself night-vison.