Originally Posted by Steve
I have had this for a while now,to be honest I find it hit and miss sadly more miss,re.its accuracy.
Have you tried the new version 2.0? It has been completely rewritten and gives quite consistent results. Now you even don't have to hold the card against a screen, a white sheet of paper under the card is usually sufficient.
Using iPhone camera it is difficult to take a photo without perspective distortion, but the new version is warping perspective before processing and the error is usually below 0.25 mm.