As an Arbitron PPM™ panelist for two years, I gotta say it: my mind wandered. How could one game the meters if one were to want such a thing? How could you make it so you get to listen to one thing and have your meter listening to something else?
My favorite is the Portable Pussy Meter (as demonstrated above by our longsuffering kitty, Butterdish). Nothing to it: clip a meter on the cat's collar, put NPR on the radio, and leave for hours, days or weeks. (Don't forget the food & water) We hear that dogs are even more cooperative doing meter duty.
The clunky Arbitron contraption for metering panelists using headphones (in the middle of the picture below) is ripe for mischief. It's easy: put the meter into the device, plug in the Walkman, tune it to NPR or whatever you want Arbitron to believe you're listening to, then simply forget the headphones, and listen to a guilty pleasure like The Ron & Don Show (KIRO m-f, 3-7p).
(Photo: My meter is listening to the fine strains of Classic KingFm, but I'm listening to John Gibson (KTTH m-f, 8-10p) but tell no one...)