As said previously by others, its only as good as the data input into it. I've always found it accurate to within 0.5 yard. I don't know anyone who can genuinely say that they can accurately range find to 0.5 yard!
The iPhone App is very useful but personally I find it a lot more user friendly on the PC.
Steyr LG110 Hunter .177 - MTC Connect
BSA R-10 SE Super Carbine .22