My Fenix HL-50 (I guess that's the number) headlamp lets me see cats at
night. I was ready to feed the neutered outside cat. The only way I could
tell it was there (two yards away) is by the bright reflection of my
headlamp on its eyes, without even pointing the lamp directly at the cat.
Probably the frequency of the LED that illuminates cat's eyes.

They would probably be useful for people who do catch, neuter, and release,
to help take care of colonies. It's like x-ray vision.