I'm going to guess it was something along the lines of this [0]... wow now I kind of want to buy one of their larger versions for the back of my car to remind tailgaters "Yes I CAN go even slower" when I'm already going 5-10mph over the speed limit

[0] https://amzn.to/3GiMXaA

Yes, exactly. They are basically all the same and use the same app.