Using a piece of acrylic which is tinted blue, can create a reflection that looks like double exposure. If you hold it up to the camera it reflects what is happening on either side of the photograph in one image..here are some examples....
I have been working on my scanner cam-web cam that is going to be a live prototype in my space in the show. It scans the space when someone comes within a 80 cm of my space and then it automatically will print them a post card (which will be my business card).