Do you actually need to prick for that? Both fingerprint scanners and thermometers (cf. http://en.wikipedia.org/wiki/Mood_ring http://en.wikipedia.org/wiki/Mood

Do you actually need to prick for that? Both fingerprint scanners and thermometers (cf. http://en.wikipedia.org/wiki/Mood_ring http://en.wikipedia.org/wiki/Mood_ring) already exist; analyzing reflections of the finger may provide even more information. A computer that doesn't work when the users is stressed is still going to get defenestrated, though.