Don't do additional work only to relase it earlier. I'm patient and can wait until you're satisfied with your code.

I have a other and better Idea to budget your time instead of packaging a minor relase...

What about creating in the opposite a lock screen mode? (if possible)

If the user locks the screen itself while your application is running start a background measurement as soon as the user has pressed the camera button (full press). You could indicate this with a sound. And every time the user make a full press of the camera button take the time (with a click sound as response) and as soon as the user unlocks the screen the background measurement is finished.
Okay. A lot of work and I do not need it myself. But I guess the best way to implement a good stopwatch for sports where you have to look what you try to time and not at the screen of your mobile.
But I don't know if it is possible to query the camera button during the screen is locked. Perhaps there is during this time no D-Bus Signal to minimize battery consumption. I don't know.