Whenever you raise the subject of telepathy and other “new age” phenomena around reasonably educated people, someone always comes back with an excellent question.
“Has it been tested by a professional magician?”
James Randi is the originator of this important point. The idea is simple — a scientist can see “psychic” phenomena and determine, is this effect statistically significant. But the magician knows how to FAKE these things, and can tell if it’s a fake… which it so often is.
So you really need a magician’s eye!
Nevertheless, I’ve mentioned before that telepathic effects have been shown “in the lab” using cell cultures that presumably don’t play tricks. 
And you can safely bet that the security implications of this family of phenomena are being actively exploited, if they exist on a human scale.
So, have the human-scale effects passed the “magician test?”
In 1891, a Polish engineer and psychologist named Julian Ochorowicz published a scientific look at a phenomena dubbed “mental suggestion” —
the ability of a hypnotizer to influence subjects on a mind-to-mind basis, without the use of his or her voice.
As part of this phenomena, it is possible to steer the hypnotized* subject from a distance, e.g inducing them to show up the experimenters’ apartment without notice, simply by heavy concentration.
* “magnetized” is the term in the parlance of the book, but modern hypnotism is a sort of melding of what was in 1891 considered hypnotism and what was considered magnetism.
The existence of “mental suggestion” caused quite a stir in the late 19th century, and Ochorowicz catalogued tests and research that had been performed by hundreds of different doctors, psychologists, and interested people (including himself, as he applied it for treating patients as a psychologist).
One of those experiments involved none other than Jean Eugene Robert-Houdin — the father of modern magic as we know it. Robert-Houdin was such an important figure in the history of magic that it was due to him that Ehrich Weiss adopted the stage name Harry Houdini. 
One of Robert-Houdin’s specialties was, in fact, faking telepathy using side-channel communication while onstage. (By changing one word or the other to a synonym, he could convey to the assistant whether he was holding a coin or hankerchief or whatever.)
Robert-Houdin also spent quite a bit of time travelling through towns where “magnetizers” had performed… taking great joy at counterfeiting and often surpassing the feats of what he regarded as charlatans.
I was therefore most interested to read in Ochorowicz’s book (starting on p. 189 (using the numbering system of the text, not the PDF)) that Robert-Houdin had been part of some of these “mental suggestion” experiments, as a sort of expert witness.
The experiments used Robert-Houdin’s wife as one subject, and a “somnambule” (practiced hypnotic subject) as the other. (They were testing the ability to simply read minds, rather than remote control.)
After the somnambule was able to pull his wife’s personal history, determine the contents of a box another skeptic had brought to the test (and tell the history of the medal inside it, which only the skeptic knew), Robert-Houdin certified the experiment was the real deal… stating:
“I was amazed, confounded. Here was neither trick nor jugglery. [In this] I would have refused to believe, had not the facts come under my own eyes.”
In a later trial, the somnambule appeared to read information about the sender of a letter direct from Robert-Houdin’s mind.
Ya think there might be something relevant to security here?
No, I personally have not tried to mind-control people on the street in order to test whether this stuff works. (Sorry, research ethics —
running around with a bunch of consent forms is not something I have the time or inclination to do.)
Nor have I been party to any properly blinded experiments to see whether Ochorowicz was making stuff up. But… I have done a fair bit of research and found that Ochorowicz’ claims are backed up by other sources from around that time, so at the very least everyone else was making stuff up too.
In other words, even if I can’t say this is proven without a doubt, I think I’m justified in viewing this as very plausible.
Anyway, given the likelyhood that this sort of thing is being actively exploited — it’s been around for over 120 years, after all — a few observations.
1) What does it feel like to be on the business end?
One of the most interesting aspects of “mental suggestion” is the ability to remotely produce what would today be called a post-hypnotic suggestion, e.g: “tomorrow morning you’ll leave your laptop behind,” or, even more offensively, “your life will start collapsing.”
Based on my research, I would suggest that on the receiving end, someone who is reasonably clear-minded and aware of the possibility could detect this.
Perhaps in the form of a “very quiet thought” intruding into the general milling about inside the head, with the result that the subject finds themself thinking, “I’ll leave my laptop behind tomorrow morning.”
I would also suggest that this phenomena is most effective (security-wise, not scientific investigation-wise) when it takes place as part of an otherwise innocuous conversation, as even a very short exchange might produce enough of a rapport and allow other nonverbal signaling to augment the effect. Plus, most people don’t think “is this person messing with my mind?” in the course of a normal conversation.
Of course, everyone’s mind works differently, so the fruits of my research in this field may not apply to everyone. Grab a friend and experiment 🙂
2) So what do you do to defend against this kind of thing?
Sadly, this is not covered very well in this particular book. Ochorowicz does offer one example — a woman who did not want to be “hypnotized at a distance” was able to reliably resist the impulse by dipping her hands in cold water.
A number of trials revealed that either washing in or drinking cold water allowed the patient to “free herself” fairly reliably. Exactly why is not clear, but given the efficacy of cold water as an alarm clock, I can guess why it would bring someone out of a trance!
Presumably other mental-self-improvement methods would serve well here, too.
 Blake T. Dotta, Carly A. Buckner, Robert M. Lafrenie, Michael A. Persinger, Photon emissions from human brain and cell culture exposed to distally rotating magnetic fields shared by separate light-stimulated brains and cells, Brain Research, Volume 1388, 4 May 2011, Pages 77-88, ISSN 0006-8993, http://dx.doi.org/10.1016/j.brainres.2011.03.001.
Just wanna translate something for y’all.
“Appelbaum: My mother [living in the US] was sent to jail for 18 months over a fight with her neighbors — without a trial. While she was in prison, they interrogated her about my role in Wikileaks. This had nothing to do with the reason she was arrested. Later, they sent her to a mental hospital, as they’d declared her mentally ill. They gave her psychiatric drugs and questioned her again as to my role in Wikileaks. […]
I myself am the target of a [COINTELPRO-style] program. An FBI employee told me how it works. […]
They install long-life bugs in the house of the target, that last up to 10 years. This is technically fascinating: they’ve managed to collect energy from the environment, so you don’t have to change the batteries.”
I should note the bugging technology he talks about has been rumored to exist since at least the ’90s. My guess is, they’re attaching a full wave rectifier to a long wire (vertical) antenna — you can get a surprising amount of power this way. Unfortunately Appelbaum didn’t go into more detail about the rest of the COINTELPRO operation, just the bug. https://www.taz.de/Streitgespraech-zum-NSA-Skandal/!128901/
Online games are a massive target for surveillance — and a recruiting ground for informants. “According to the briefing notes, so many different US intelligence agents were conducting operations inside games that a “deconfliction” group was required to ensure they weren’t spying on, or interfering with, each other.”
Wikileaks releases an update to the TPP docs. http://wikileaks.org/Second-release-of-secret-Trans.html?update
(it’s a whole bleeding book, not gonna quote it)