Nielsen box

The Nielsen box is a mysterious and arcane device whose presence in your home indicates whether or not a television network even remotely cares what you think. It magically registers "viewer radiation," the invisible indication of interest in a particular program, and whisks that data away to the networks, to help them determine how much to charge for advertisements. Nielsen boxes are highly coveted, especially among rabid fans of soon-to-be cancelled shows. A special squad dispatched from the Secret Service to personally guard every family in possession of a Nielsen box only adds to its mystique, although admittedly, it makes their supposed anonymity a bit trickier.
The Nielsen box was invented by and is named for Leslie Nielsen.