I anticipate you're correct about the BreakSpeed app, but it's not crucial to success. Like CJ said, it's more about getting the "feel" than the number.
Really it's about understanding everything that affects how far the cue ball goes. I can often attain the same final CB location while hitting the CB a half dozen different 'speeds'.
Speed is easy. It's not at all difficult to hit the CB at the speed you want. You can learn to to hit a good lag in like 2 minutes.