you wont always see them, they hide them nicely, ours is in the back of our entertainment center, its about the size of an older VCR with a bunch of wires in/out of it, and a modem zip tied to it. Each box has a modem then the main box has a cellular uplink that calls out every night + uploads each days viewing data.
when my ps3 or 360 is on, they cant see whether im playing a game, or watching movies, all they know is it is on. So far its pretty cool, even though im sure my house doesnt control whether sons of anarchy will continue for my lifetime, it was just something that sounded different so i gave it a shot. Its funny though, while talking to the tech installing it, i asked him if he liked Walking dead, and it wasnt easy to get an answer out of him. They have very strict rules about not influencing what Nielsen families watch.
As for the install, they were in and out in about 3 hours, and come every 6 months to check signals. We get the occasional call if a tv is left off for a few days to be sure nothing is wrong, but its not a bother. We dont have to do anything, dont have to type in a unique personal code regularly (i heard they used to do that).
They begged us to do it, because our house was "selected" based on a bunch of different things, and they even said if/when i dont want it anymore, and i change my mind, they will pull it back out of the neighbors house and put it back in here....they use some kind of system to determine which houses are best for something.....
i jokingly asked the tech what the going rate was for the boxes on eBay, i thought he was going to start unplugging it LMAO....but i googled around, and i dont think they have much value to anyone other than Nielsen.
They dont monitor phones or wifi though, to whoever posted that...they only can see what show your watching and when....
any ?'s, feel free to ask, i actually just had a storm short out my Turtle beach headset and the HDMI 1 port on my 47'' flat screen...so gonna get em fixed this week hopefully on their tab, that was one of the perks i considered when i agreed to them coming in.