I do mentalism and stage hypnosis on the side. I know a few of Derren Brown's secrets, though I could never pull it off like he can.
To do these psychological tricks, there are several things that must be in place. For instance, you have to control the environment you are in, (i.e., a stage setting where your presence is more important than other people), you pick the volunteer, and you have to be 'on' and alert to the body language of everyone around you, and other factors...
It's a performance, pure and simple. In real life, I don't think a person can do that 24/7. It's too difficult with too many uncontrollable things going on, and sometimes one little distraction can blow the whole psychological trick.
Even Derren Brown himself said that he can't do it 24/7. He can do it in a performance easily, but when real life is occurring, he can't keep it going.
Derren is a great example of a magician, for lack of a better word, using psychological tricks. The book to read is "Tricks of the Mind", where he explains the basics of what he does. There is no woo at all in the book, and in fact, he is a skeptic too.
As to Jim Callahan, I've never liked him. He keeps claiming he has supernatural powers then claims he doesn't then challenges people who say he doesn't have powers. I deal with him by ignoring him completely.