Are implanted subdermal trackers in movies at all a realistic possibility?

We already implant subdermal RFID chips in animals and people. You just put the chip inside a non-biologically reactive substance and it's fine.

The bigger problem is scanning distance. You're limited to only a dozen meters or so if you're not using an active RFID with battery. ~100 meters with a battery but then you have to change the battery every now and then.

With present tech, I don't think so unless the area where you're being tracked is full of equipment that can read the tags (think big RFID readers like you see on the exits of stores). Unless the tracker implant is fairly large to be able to contain/harvest power to power their own active transmitter. Then it would probably be noticeable or at least uncomfortable.

I'm basing this on the fact that we chip pets with passive tags, and those don't seem to suffer any kind of rejection/infection.

Implants that don't get rejected exist. Either medical or as body art or even by cyber enthusiasts. I'd say even a piercing would qualify as a type of implant. So I guess if you know what you're doing you can get around the infection topic.

Forget that, what powers them? Something that can be read with a close by scanner makes some since since I figure you could induce a current in one, but the kind you sometimes see in movies that constantly sends out a signal that some satellite can clearly track anywhere in the world, and do so for days, weeks, months or longer, would need one heck of a battery I'd imagine? And in a very small space too

Subdermal is a lot easier than implanting in other compartments, e.g., intracranial. For example, hormonal birth control exists as an implant.

But, there's fascinating research into how the brain rejects implanted electrodes, e.g., neuralink. Lots of work has been done developing materials that are less likely to be rejected by the brain and the brain's immune system. For example, electrodes can be coated in chemicals to make them less harsh to the body, and flexible materials can be used.

We also have subcutaneous birth control that doesn't get rejected.

artificial organs, that birth control rods in the arm, I have a hernia mesh in me right now and I did not have to take immune surpressors and neither did my wife with an artificial hip (which did get infected) and screws in the knee oh and a plate in her skull. screwing artifical teeth into jaws is very common now to. Seems like a little subdermal implant would be no were near as bad as these common practices.

Many materials are biologically inert. Titanium, for example, is often used for replacement joints and doesn't need anti-rejection drugs. They autoclave or otherwise sterilise things during the operation, so the infection risk is pretty much the same as for any other kind of operation.

I think this is asking if something seen in movies could happen in real life, but I first read it as getting something implanted when going to see a movie and couldn't figure out why no one was asking why you would do this.

Yes