you kill me sometimes...... ok, X-ray glasses , are a gag.... They're just prismatic so it gives a weird effect when looking through them.
The reason REAL ones do not exist is that first of all "x-rays" are nothing more than another realm of the electromagnetic spectrum (same as light, radio, UV, ULF VLF etc) Like light, xrays are absorbed/reflected by some denser mass/metals (lead for example doesn't allow it to pass through, skin it goes right through, bone absorbs some of it) what this does is during an xray the film on the opposite side of the x-ray gun absorbs the passing rays like a silhouetted photograph (a photograph minus the reflected color we're used to) so the bones show up, the skin does not, since this is a different amount of xrays passing through those locations. Now imagine what this would take to function as some glasses. first of all you'd need an xray gun on the opposite side of the person, then you'd have to deal with radiating them with radiation that the xrays are (they're not really that safe in large doses which is why docs wear those lead aprons when they're working in an xray room) then the glasses would have to have sensors to see the xrays, convert it to visual spectrum, then you only see bones metal buttons and other crap on their body....kinda pointless right? X-rays vision a la superman is nonsense at best more useful for seeing through walls would be thermal imaging in that case, long as there is little insulation between you and what you're looking at (which tends to be a big red blob for a person) there are some sonic imagers that work pretty well for viewing inside of buildings, but they're processor intensive requiring a lot of computational power to make sense of different levels of interference by the mass between you and your viewing target as well as that which lies beyond them. I think what those units use is a harmonic sweep sonar type element that goes through frequencies hitting the harmonics of the possible types of matter between you and it's ultimate range and makes sense of how things react to this (every material has a harmonic frequency, ever heard a certain sound outside that shakes only the cd sitting on your desk, or perhaps listening to music noticing that certain notes make the crystal cup holding your water vibrate a bit? that's resonance, which is what occurs when an object is made to vibrate at it's natural (harmonic) frequency, it then produces some interesting effects, which can be used in conjunction with sonic absorbtion/reflection to determine what the shape of an object may be, it's rather math intensive and not really for this forum...here's some neat links related to harmonics though....
X-Ray Specs were long advertised with the slogan "See the bones in your hand, see through clothes!" Some versions of the advertisement featured an illustration of a young man using the X-Ray Specs to examine the bones in his hand while a voluptuous (but fully-dressed) woman stood in the background, as though awaiting her turn to be "x-rayed."
The Advanced Intelligence Company, Ltd. manufactures a device called X-Reflect Glasses which is claimed to allow the user to partly see through certain types of clothing. These goggles are a variation of thermal imaging goggles, but are intended specifically for daylight voyeurism. The device retails for US$2400 as of 2005