AZPete,
I got a Breakrak in January. I have no numbers to make you happy, only subjective comments.
First off, it does not do anything for you, that you could not do on your own, provided you are willing to wrangle rack after rack of balls. In the past I never had the patients to do this more than a couple of times and then I was on to practicing something else. The BR allows me to set it up in a minute or two, practice 50 breaks or so, and tear it down in a very short amount time. The feedback is immediate in terms of the quality of your hit. If, for example your QB is constantly veering off the right, you are not hitting the head ball squarely, but rather on the right. In my case, I was spraying them off both right and left and found I needed to slow my speed down a bit in orderer to hit the head ball square in the face more consistently. As I continued to practice, I was able to slowly pick up my speed and maintain my accuracy. My suspicion is my greater accuracy with increased speed has spilled over onto other aspects of my game. As far as squatting the rock, watching how the QB behaves off the rack allows you to fine tune your parking ability. If the QB( provided you hit squarely) rolls into the rack area, you hit with too much follow, given the speed, and need to hit a bit lower on the QB, and visa versa. The ability to do this over and over without re-racking gives me the immediate feedback I need to dial in my break. That is where I believe the benefit of the BR comes in, not the absolute break speed. We all know if you hit squarely the more energy will transfer to the rack. Subjectively, you can observe and quantify this in the way the BR behaves when hit off center. Physics is 30 years away from me now, so maybe someone else can calculate how fast the energy transfered falls off when the QB hits a mm or 2 off center. My sense is quickly.
So, in a nut shell, The BR helps you diagnose aiming issues as a function of speed, and fine tune the follow needed, given your break speed to park the QB in the center of the table. You could use it to calculate speed with the app you mentioned, but you could do that with any rack of balls.
Good luck, Steve