I just checked out the new version's screen shots at the app store. Apparently, he is using the serve speed formula at http://www.donthireddy.us/tennis/speed.html
which I told him about. The numbers all check out. This means the serve speed estimate should be very accurate.
The OP has finally turned the app into a useful tool by calculating the initial serve speed. I will be buying the app soon.
If you are just curious about your serve speed and are not interested in doing so on a regular basis, you can just record the serve and plug in the numbers into the website link above. That will do roughly the same thing with less accuracy.