They are Sonic Animal Repellers, less than $5 from SCA. And I also get a warm and fuzzy feeling that they work.
It has been over 20 years since I hit a roo ( Yes, really, Mr. Murphy, twice in my HQ which I didn't have them on ) back in the olden days when I used to drive to work on a dark, lonely road.
With them fitted since then, no problems.
I put them on my mate's LandCruiser before we went Birdsville, and he just laughed. No animals were harmed during our trip.
But they do not work on cattle. They see you coming, walk into the middle of the road and stare at you. Maybe the Repellers make them inquisitive.
For $5 they are worth a try, and you can report your conclusions, or collisions.