Hi Karen,
There is a bit more to consider. The glass has to be a special type of glass that will not distort or affect the image of the tv. You also have to consider ventillation in most instances. For most regular types of flat screens, go to www.mediadecor.com
You can also look into another company that produces low voltage televisions. These tv's do not produce much heat and are constructed to withstand the little heat that they do generate. Go to www.adnotam.com to check them out.
Either way, it's an expensive venture and this type of solution is really worth it in cases where hiding the tv is important. You can always try to source out a low cost solution using a regular one way mirror. I'm not sure how well it will work. It may be worth a try.
Good Luck!
Ramsin
www.khachi.com