In the context of having a easy to use method of recording data, photos, etc. the smartphone would be a great choice for the range. Otherwise a more bulky paper recordbook would do - which is still the format of choice for professional shooters who need to document settings and results. And that notebook has the ability to work without power, in a remote location, and has a low probability of disclosing the covert location of the user.
It won't go beep at the wrong moment, or have a starburst screen. In civilian use, they get treated a lot better.
On the other hand, I would not be surprised that 95% of the shooter programs are little used showoff apps for wannabes, much like dyno programs or fantasy sports teams. The legitimate users keep quiet about it, because so many posers have made it laughable. While there certainly are serious smartphone users, the majority I've seen are simply social enhancement and entertainment devices for those who can't face the quiet boredom of reality.
Given the requirement, I would just hop down to the Post Exchange and pick up a Write in the Rain notebook, format the pages as recommended by the pro's, and move on. I don't think an app will be a good method of recording info longterm over the years I might shoot that specific weapon. The phone is likely to be obsolete along with the app much sooner than the gun.
Android apps are written in Java, which is limited in Iphone. I have been looking for them for my cheap bling feature phone, and there's not much out there to impress yet.
