I literally went to the eye doctor yesterday for an eye exam and got my prescription for them. The PD measurement I received from this app was only .1 off of what I received from the doctor. That is a negligible amount and honestly the discrepancy could have come from anywhere. So the app worked for me as promised.
HOWEVER (and this a HUGE "however"), be extremely careful with what type of card you use for the picture. DO NOT USE A CREDIT CARD!!! That is a pretty simple way to get your identity stolen. I used an old hotel room key I still had in my wallet and received the results I mentioned above. Do not get yourself into trouble with this app.
All in all, worth the 99¢.
antsy89 about Pupil Distance PD Measure, v1.2