I recently got the BulletFlight app for my Iphone, and like it so far. Very easy to use and saving entires for different loads for the same rifle is simple. Once you get your atmoshperic conditions put in you can switch to a Heads up Display that allows you to switch range and wind speed/direction very quickly which is nice. I got the $29.99 version (they call it their military version) which takes into consideration coriolis and spin drift. Only thing is I didn't see a place to imput twist rate, which i thought was needed to calc spin drift. I've only had it for a couple days and haven't compared it to other programs, but many on here have said it was spot on with Exbal and others. Can't wait to try it out in the field. The BulletFlight app seems to be the best option out there for the Iphone.