Devices for determining pitch speed.?

I have tried speed balls and they generally don't work very well. When my son was younger I used a glove radar as a good way to track speed differences between pitches and his relative progress. I had good luck with it and used it for several years.

The Radar Glove is a good inexpensive device. It is relayively accurate but requires some calculation to get the fast gun read that you get from Jugs. It is for younger guys and is a fun thing to use. Also the cather must keep his glove steady to get best readings.
I bought several and sold them all for a profit. Might be worth doing. I made a deal with the owner so it didn't really cost anything in the end.