If you're the official statistician for your team, the first thing I'd recommend is to get off the sidelines and find a seat near the PA announcer and scoreboard operator for home games. That way you can see better (higher angle), and can relay accurate info to them. For road games, try to get a seat in the press box or coaches box, if available.
If you use an app, remember that you get what you pay for. Free apps will probably be limited as to what type of info you can input, and how detailed you can get. If there's a demand from your AD or coach for immediate/"live" stats online during a game, an app will be your only option. When I worked alone, I used paper (graph paper made for easy layout), and just developed a shorthand play-by-play system that could be easily tabulated after the game.
The absolute ideal situation is two people, working from an elevated position. One person can call/spot what's going on, and the second person can write/enter data. That way there's always a set of eyes on the field, and less chance of missing something (e.g., who forced that fumble, who tipped that pass). Obviously, at some schools that isn't possible due to lack of personnel and/or lack of space.
