I think if this were happening, people would eventually be able to tell by watching the network traffic. You may not be able to decode the network traffic, but

I think if this were happening, people would eventually be able to tell by watching the network traffic. You may not be able to decode the network traffic, but if you run it through an analyzer like wireshark, while you say "OK, Google" and you see the bandwith increase, then if you see a similar bandwidth pattern other times you might have a clue that its recording. Of course that assumes they aren't saving to the disk and sending it later.