A fellow parent showed me The Baseball Radar App by studio S software. It is a fun app to use at a game to determine pitching velocity. You set the distance of the throw for the app to work. There are a variety of presets including baseball, softball, little league, pony league, bronco league, mustang league, pinto league, coaches pitch, and softball (16 U). You can also set custom distances. Simply tap start when the ball is released and stop when it is caught. The app will configure the speed from those calculations.
I used this app during a practice while the coach was using a radar gun. The app was pretty accurate.
Give it a try!