Just an interesting aspect to discuss:
I am currently thinking about a possibility to track emotions by measuring vital signs...actually what comes to mind and has been done recently is tracking skin conductance and heart-rate variability. These indicators are known to measure arousal.
But is it possible to not only measure the mere existence of arousal but also the direction? How could you decide whether the reaction is caused by stress or euphoria?
In my opinion this is hardly achievable...What do you think about that?