Caldwell app.

Ive owned A Caldwell chronograph for a few years now the reason I bought it was because of this app. I use it on my iPad mini not only does it record all my shots velocity but power factor as well. Once you set up the bullet type your using, it automatically puts in the ballistic coefficient allowing the app to add other information. I like the ability to photograph your target as well so you can see how well you did later on.

Skyscanner about Caldwell Precision Chronograph