So the letters in the mail are different than being a full fledged Neilson house.
If you want to do it, they will come out and install boxes on your TV's, Computers, etc. Every time you turn the TV on, you will just push a button for who is watching...So 1=Dad, 2=Mom, 3=Kid #1, etc.
We got a check every 3 months I think...And after two years got a couple grand worth of payments for doing it. Not to mention the random drop in's by the local rep who would bring over a cheesecake and a $20 bill just to say thanks. Felt really odd the whole time, but I really have nothing but good things to say about them. They know they cant provide data without your input, so they are very appreciative for you cooperation.
Ask away, I think I got a pretty good grasp on the whole concept.