I added a LED strip light to my press a few years ago.
It's there to shine light into the cartridge case in the step after powder is dropped in and prior to bullet insertion. That way I 100% visually inspect the powder level.
Here's a demo video:
https://youtu.be/hIraXq6u0VY
Last year I added a finished cartridge counter. It uses a magnetic reed switch that is actuated by the bullet in a completed cartridge at the taper crimp stage for pistol cartridges like the 9mm and .45acp:
https://www.youtube.com/watch?v=Vyh-Lp2FziU
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Igitur si vis pacem, para bellum -
- Therefore if you want peace, prepare for war.