This product would be handy on toll roads that use cameras to bill you. Like the 407 in Ontario.

My somewhat educated guess is that the product would very likely be illegal because the flashes intentionally obscure the license plate from being recorded and that is the part of the laws in most states, provinces and countries this falls foul of. Most of the laws are written in such a way to say that any attempt to obscure the license plate is illegal. That is usually meant to suggest mud, various coverings and so on, but can depending on the specific law, mean any attempt by you the owner or driver of the vehicle to obscure in anyway, the recording of the license plate by authorized agencies or companies.