Home sellers are now using interior security cameras to record video and audio of buyers viewing their homes and taking what they collect in to consideration in sales deals. Some are watching buyers view their homes in real-time, using cameras linked to the buyer’s smart phone. Such data may be used by sellers to discriminate against buyers or seek higher prices (such as if the buyer was enthusiastic while looking at the home).
This is a mine field of potential discrimination cases, and in some states, recording audio of someone without their permission is a felony.

The trend has spurred what Joan Rogers, a broker with Windermere Realty Trust in Portland, Ore., calls a “Hey, be aware of this” conversation among her colleagues and counterparts. Rogers says the discussion started in her area about three years ago, “about the same time that integrated home media and security became a thing, with devices that could record your home and report back to you on your smartphone. The conversation started happening that it would be wise to watch your mouth because you just never know what device might be recording.”

Source: Home sellers now use spycams to gather intel on prospective buyers – MarketWatch
Advice: When shopping for a home, tell your broker only what they need to know and nothing more. All they need to know is what type of property you are looking for and that you have sufficient funds or financing to buy the property. Anything else may be used against you in the transaction. We live near Portland, Oregon and our buyer’s agent provably shared confidential information about us with the seller’s agent, who shared it with the seller. We know this because he was dumb enough to cc us on the email he sent to the seller’s agent.
Now, add that when looking at homes, you must say nothing and show no emotion. Take written notes and photos but reveal nothing. Assume the seller is spying on you.