I use it when practicing tennis serve.
When tennis serve enters, click "in button"
If faulted, click "fault button"
If you make a mistake, click "return button"
To start over from the beginning, click "Clear button".

It's a tool I made for myself, but I did not have a similar application, so I upload it.
It is a simple application, but since it is spending time as it is, it is charged.