Well now there is:

Facial recognition

FingerPrint recognition

Voice recognition

Iris recognition

DNA recognition

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I wonder if it would be possible to have brainwave recognition, body electrical activity recognition, aura recognition (infrared (?)), body motion recognition, Etc.

While I understand the general idea about those things, I am not an expert on any of them.

Governments (those in power) can use the stuff.

Law enforcement can use the stuff.

The ones called criminals (mafia), including drug lords, can use the stuff.

The so called private sector can use the stuff.

Terrorists can use the stuff.

And private people can use the stuff.

But without proper databases and equipment can't be used.

Some of this stuff, we see on T.V. shows and on movies sometimes.

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Privacy? With so much crime and terror, there can't be privacy, but more often than not >

Those in power are the ones who are the criminals and the terrorists.

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About private communications, while you can't keep some from seeing and hearing what you say, hear, write and read, you can "code" the stuff, so "they" won't know what you are sending and receiving, it is not true that "they" can decode everything that is coded, you just need to know how to do it right.

But I am not really one who can be called an expert on such things.