If you think a lie detector it is to expensive for you, then why don’t make your own device?
You can’t get more simple than the Galvanic Skin Response GSR sensor. It is just a cut 9V LEGO motor wire and some aluminum foil wrapped around your fingers with tape. I was inspired by talks by Mindfest panelists Karen Wilkinson and Mike Petrich who talked about using this type of sensor. I’ve also found out that the Media Lab at MIT has a program called the Affective Computing Research Project that also uses this sensor.
It is popularly known as a lie detector, but is also used in Biofeedback conditioning. The theory is that; the more relaxed you are the dryer your skin is and so the higher the skin’s electrical resistance. When you are under stress your hand sweats and then the resistance goes down. The range is reported to be 5K to 25K Ohms, but I’m not sure where the measurement was taken. 5K would relate to a RAW reading of about 340, while 25K should be around 730.