BDC for sure... if not for the app alone...
At the range, I have 50, 75, and 100yd targets and I use the Nikon SpotOn app on my iPhone to calibrate. Super easy to use and now I consistently hit 3-inch metal targets at 50, 75, and 100 in one magazine without having to turn dials and recalibrate anything.
I am using the ProStaff 4-12x model
Some screenshots of the app. You can pick everything from the type of ammo to what distance you zero to the ambient conditions...