Stress biofeedback card, we also call stress control card, mood card or lover card.

Usage:
Hold your thumb onto the Stress Control Card indicator for about 15 seconds, until it changes color.
Blue - you're calm, Green - you're normal
Red - you're tense, Black - you need a vacation!

Detail:
It can be designed by Regular credit card size or other shape, it is made as durable plastic temperature indicator. A liquid crystal square changes color as it is warmed by the finger, indicating Stressed, Tense, Normal or Calm.

Anyone having anxiety can benefit from the Stress Control Biofeedback Card. Makes relaxation training fun and inexpensive. Credit card size with black square that changes color on touch. Relaxation techniques on back help turn card blue (most relaxed). Builds in automatic relaxation response when stressed. Lessens anxiety-caused headaches, HBP, insomnia, smoking, overeating.