Originally Posted by Grubrunner
GPS/satellite is dependent on an externally mounted antenna. It has nothing to do with your vehicle's glass or what's on it.
This may be true for you, but not in general. I use both a GPS device and a satellite radio device that sit in the car / mount to dash. Neither has an external antenna.
I do agree performance of these devices or cell phones is unlikely to be affected by window tints, and has never happened to me. But it has happened to some, and some manufactures put the warning on their products if they contain metallics.
I just had my wife's car tinted and opted against a particular tint that carried that warning. Unlikely? .....sure. Was I going to take a chance? I decided not to.
I do believe that was what the op was inquiring about.