What happens when a GA pilot squawks 7500?
Who would shoot you down and why? You are in the middle of nowhere. Who are you endangering? ATC would try to contact you to ascertain your actual condition. You may have accidentally put in the wrong code. They would then offer assistance if needed. 

If it was a kidnapping situation, all they could do is follow or track you until you land. You are not going to get far. Even if you went to another country close by, you can still be tracked and local authorities alerted.