A few years ago at the T1 North showcase a couple of obnoxious dads had their "guns" onsite and making under the breath comments on many players. It was rude. The next day my wife and friend sat behind them with their hairdryers. When these guys pointed the wifes pointed and did they get a laugh. The guys tried to move and they were told they were being shadowed until the gun went away. A sight to behold.
I can see where guns can be a useful tool. I would find it interesting to collect data from not only my kid but any other on his tean that would like to see their progress charted. You just have to remember that you are not looking at speed but the relationship between innings, velocity, and specific pitches. This is the type of knowledge that a pitcher needs to understand in order to improve.