All humans who have alien contact get implants.
They are like tiny computers that do everything you can think of and more.
They are not a tracking system.
They always know where we are.
They mostly monitor things in our bodies, normal things we know about well, and many other things we don't know about.
If we could go to our doctor and get hooked all up to many machines that could test everything in our whole bodies at once, that's what an implant can do.
The machines measure vitals and effects in our bodies.
The advanced races measure and monitor all of that, but also many kinds of things we don't even know about in our bodies.
Usually they are monitoring our bodies physiologically.
Some are permanent, most are temporary.
The permanent ones are not detectable.
They are made of all different materials, many of them are made of organic material and dissolve on their own once they've done their job.
Most are put in our physical bodies, some are put in our spirit bodies.
Choice
You always have a choice.
But if you went for a check up to your doctor, you would not get there and refuse to have your temperature taken.
Especially when they are working with us, they are careful to know how it is affecting us.
This is in all ways, all functions of our body, mind and spirit.
Stress is like a disease in itself, and meeting alien life is very stressful, even when we don't even know we are doing it.
It's a choice from before our life even.
With implants, they can monitor us from a great distance. We don't need to be taken up for a simple check.
Detection
If you have an implant from alien life, it belongs there until its purpose is finished and it would be very difficult to find.
If you found it, it would move or dissolve before you could remove it.
Implants from alien life are for many different things, mostly for monitoring and measuring natural systems of the body and spirit body, some that humans know of and some we don't.
They are not placed randomly for the purposes of healing or for tracking.[1]
Removal
I don't think most of what you hear about having implants removed is true at all.
A real video of a real operation to remove a real implant from real alien life, would not be allowed to be shown in public.
But if somebody wants to discredit the facts of real implants by real alien life, all he has to do is make a video of it so that it can be debunked.
Actors make lousy videos so that nobody will believe any similar stories.
Conclusions
None of the visiting races experiment on any humans - they know exactly what they are doing.
Contactees are periodically examined medically, and tested mentally and for natural abilities.
Contactees periodically receive implants from their alien contacts; most are temporary and some permanent.
They are not put in the brain.
The implants are for monitoring of body functions mostly, and never for tracking.
The alien races need no kind of device to keep track of the whereabouts of their human contacts.
Our leadership of Earth uses well-known true facts that they cannot cover in creating stories of abduction to "implant" and maintain fear and mistrust of all other races in the minds of humanity.[2]