On an unrelated note, if you have verizon FIOS they can push a new firmware package to your router and reboot it easily, without you ever knowing. And they log in every day and confirm the hash of the firmware you're running - if it's not on the approved list (which is generally just the current one they have you set for) it automatically reflashes. A properly written firmware could monitor not just all traffic that was internet bound, but also everything on the local lan and wireless net.
At least in the router I have, there is a significant amount of dark radios on the board. There's a second (unused) 802.11n radio that in other editions is used as a second n stream but easily could be used to do full site surveys or packet capture or as an evil twin, a DECT (cordless phone) compatible phy that could impersonate a cordless basestation and if I read the spec sheet right a bluetooth and powerline phy.
The verizon STB for their converged QAM/IPTV also downloads a portion of their firmware from the management servers and verifies hashes and oprational state TCG style - if they aren't connected to the network they will never actually finish booting.
Details are limited about what the CISCO built STB contains on the inside, but it at least has a light sensor (ir remote) and a vibration / accelerometer (for sudden drop hd head park) that they have been touting as a feature that allows them to measure ad exposure based on floor vibrations that suggest you walked away during a commercial.
They've also been recently touting a 99% effectiveness rate at uniquely identifying the viewer in multi person households based on statistical modeling of the order and speed buttons are pressed on the remote, though I'm unsure if that's with the current cisco gear or the new motorola (google) gear that they are just rolling out.