A lot of fiction is based on fact, the author just uses a little imagination and 'what-if' to write the story, to make it interesting and entertaining. I think where a lot of people get confused, is where they see the similarities in a work of fiction, and the actual science. There have been quite a few fictional devices, that have actually been realized. Who would have imagined a video phone, let alone one you could carry in your pocket or wear on your wrist, 30 years ago... Comic book stuff, and now common place.
But there are many things, that will never be practical in reality, but do exist to some degree. EMP is destructive, and not very selective, so it's doubtful anyone is going to do much development. If it were promising, I'd think somebodies military would already have it. Also, nothing is free, you get less power out, than you put into it. Most everything these days, has some sort of protection from Electro-magnetic waves, since we are flooded with them. We pass by powerful transmitters all the time, and it doesn't kill our cars, or other electronics, so how much power are you going to need to get any useful effect?