eso estar uno desparchado, lo encontre muy rapido en google, palabra clave a buscar ¨pantalla transparente¨. y es el primer link que sale
aca el link de las imagenes
http://www.flickr.com/photos/w00kie/sets/180637/
y aca una comunidad francesa dedicada a ese cuento
http://www.macbidouille.com/
y este es el foro de esas creaciones.
http://forum.macbidouille.com/index.php?act=module&module=gallery&cmd=sc&cat=11
aunque ahi explican algo sobre como lo hacen, pero no estoy muy seguro.
this is a photograph trick.
1st- with a tripod take a picture of your desk without the computer on it.
2nd- take a picture now with the computer on the desk.
3rd - open both pictures in photoshop and paste one of the pictures over the other as a new layer.
4th- make a selection of the area of the computer desktop and copy it from the image that has no computer.
5th- the image might be skewed due to screen positioning. Use the free transform funtion and drag all corners of the selection to match the picture canvas.
6th- use this image as the desktop in the computer.
7th with camera still in position, take a picture and the illusion will be created.