Your tone was misunderstood. We might say email is affect-limited. We cannot even agree on the physiological response from person to person. Lie detectors can be fooled, yet a friend can usually catch you in a lie. Recognizing and understanding emotion is both possible and meaningful when the process relies on knowledge of a particular person.
Sensors exist that recognize changes in facial expression, heart rate, blood pressure, and more.
Add pattern recognition and learning, and a computer could begin to understand a particular person's affective state. The results will be personal, not universal, and that is the point. They will not be restricted to perceiving only the visible and vocal forms of affect expression but will have the capacity to get to know you. Interactive games might detect your level of fear and give bonus points for courage. Instead, the biggest peak, significantly higher than the others, occurred when the student had trouble configuring the software.