We receive calls almost daily asking if we offer films that will allow one to see outside, but block the view from the outside. The short answer is Yes. However, there are few things to consider. Most films will create what we refer to as "daytime privacy". This means during the daylight hours when it is brighter outside than inside, the film will restrict visibility from the outside while allowing for a clear view from the inside.
Unfortunately, at night... this all changes. When it is dark outside and the lights are on inside it will be easy to see in through the windows. This is simply the physics of light. Darkening the glass helps, but you can still see in.
http://www.tintcolorado.com/ for more information.