Hi DBate. Unless your airline/operator and government agency has approved iPhones & iPads on the flight deck for operational purposes, you must cross check any data from these devices with your carriers approved documentation. I always have my F/O go through it manually through the approved charts to confirm my results ( just to be legal )!
I have never found a descrepency and I had 7 line pilots ( including two check Captains ) beta test the app prior to release.
As a matter of fact, one Check Captain uses it while running the simulator to make sure the guys up front achieve the correct results !