They're little computers with cameras that capture everything. I think some of these types of devices run Android. Many are very poorly secured, like the article suggests. A "license plate reader" sounds like it only reads license plates, these are surveillance platforms, with cameras and microphones. They can be accessed remotely to do more than just read a license plate.
I'm thinking the person says that couching it as a license plate reader is disingenuous, because it doesn't really convey the gravity of what the devices are capable of.