In one set of patent applications, Amazon describes how a “voice sniffer algorithm” could be used on an array of devices, like tablets and e-book readers, to analyze audio almost in real time when it hears words like “love,” bought” or “dislike.” A diagram included with the application illustrated how a phone call between two friends could result in one receiving an offer for the San Diego Zoo and the other seeing an ad for a Wine of the Month Club membership.

Some patent applications from Google, which also owns the smart home product maker Nest Labs, describe how audio and visual signals could be used in the context of elaborate smart home setups.

One application details how audio monitoring could help detect that a child is engaging in “mischief” at home by first using speech patterns and pitch to identify a child’s presence, one filing said. A device could then try to sense movement while listening for whispers or silence, and even program a smart speaker to “provide a verbal warning.”