I noticed something on a CO Highway Patrol motorcycle helmet yesterday. His helmet at a glance looked like a typical flip up, but I noticed as he passed by me the helmet seemed a bit large (in volume). I passed it off as the officer leaving the chin bar and face shield 'up' (why do they do that??). I shook my head as I also saw he was wearing light gloves, light pants, short sleeve shirt, and no jacket. (Seemed less than suitable, but oh well.). The rear of the helmet had a large dark area (a bit shiny like a smoked lens) from mid-elevation down to bottom edge. That smoked area was integrated into the shape of the helmet with no protrusions or obvious stick-on devices.
I happened to follow for a few miles, at which point I noticed the rear smoked area of the helmet seemed to flash for a moment--not very brightly though, and so I thought it was a reflection on my windshield from another vehicle's LED light strip that happened to superimpose over my view of his helmet. But it caught my interest. Watching further, I noticed that when the officer moved his head, the LED strips would flash for a few seconds, but rather dimly. I didn't see the officer brake so don't know what it would do, then.
The lights were two vertical columns of small red LEDs, each perhaps a dozen or so LEDs spread over about 4" height, the columns perhaps 2" apart. The two columns wigwaged several times a second for a few seconds, then stopped. The light strips weren't crisp and attention getting, but were a bit subdued.
Being away from riding for a couple years now and unaware of them, my thought was "good idea, poor implementation."
I can't find online in any pictures or matches for what I saw.