And double-check that it isn’t an HDMI cable with ethernet, and a computer that ‘helpfully’ uPnPs the TV to the internet, yes?
And, with with basic GSM phones retailing for $12, no contract/bundle, quantity one, better sweep for unexpected GPRS chatter as well. (Only some data would be worth the transmission cost, in that case, since they can’t just piggyback on your internet; but if Amazon could do ‘whispernet’ a compressed summary of your viewing habits every X days could probably be done pretty cheaply).
Contemporary MEMs mics are god’s gift to paranoia. High sensitivity, omnidirectional, all ADC handled in-package for a nice low-pin-count digital output, 4x3 mm square, 1mm thick. Doesn’t use much power either, so good for battery powered applications. The ones that hand off analog functions can be even smaller (Mr. 2F17 045, in red, is the mic in those ubiquitous Apple earbuds-for-chattering-with, it even functions inside a fully enclosed plastic housing, no mic hole/grate/etc. Vendor/datasheet unknown, at least to me.)