The US Department of Homeland Security (DHS) is making quick progress on its Future Attribute Screening Technology (FAST) or Project Hostile Intent as it was called originally, which is designed to detect hostile thoughts, or thought crime as it's known in Orwellian-speak.
The technology uses high-tech sensors that can measure breathing and pulse rate, as well as facial expressions and skin temperature in an attempt to identify people acting suspiciously. The system aims to make it easier for border control staff to choose who to single out for a probing interview.
FAST has only been tested so far on paid volunteers, of which, some were instructed to "act" shifty. I would imagine the physiological symptoms that result from real world intent would be quite different to anything that could be simulated by actors. These symptoms could also easily be altered with drugs, both legal or illicit.
I can't imagine this system ever achieving a low level of false positives. People will naturally show signs of stress and irritability from very common everyday conditions such as sleep deprivation, nicotine withdrawal or simply from having too much coffee. That is all before factoring in medical conditions or any emotional aspects that may cause our bodies to act in a manner that may seem suspicious.
Impressive technology, but it is unlikely to ever be more helpful than the notoriously unreliable polygraph test.