I see what you mean. What if you are in terrible pain and "computer says no".

I don't know how well this works, and if all bugs are ironed out. What if it does't work for tall or chubby folks? In a way, maybe we would be rather good testers - we surely don't lack our moments of pain...

Also: I'm going through a phase where one hour I feel absolutely fine, and the next I'm in serious pain and suffer from quite severe cramps. The yo-yo effect almost makes it impossible to answer the question "how do you feel today?" Not sure how this device would fit in. Maybe it would display "Wimp detected"