With hundreds of short-term rentals here in Nashville, many property owners do have surveillance cameras both inside and outside their home.
After the couple found the hidden camera inside the fake smoke detector, they called police.
Police later arrested 56-year-old Wayne Natt and charged him with one count of video voyeurism.
"If you do have consent of the people that stay there and I think you're covered but I think it's a better practice to not do that," Newschannel 5's legal analyst Nick Leonardo said.
In 2010, Tennessee passed an Electronic Surveillance And Wiretapping Act. That law makes the kind of filming Natt is accused of a crime, making him subject to a civil penalty or lawsuit.
"When you rent your property out, be it short-term or long-term, the people that you rented to have legal rights (to know) and they don't forfeit those rights simply because they're renting your space," Leonardo said.
Natt told Florida police he had cameras in his condo for personal reasons -- to record sex parties -- and he had the consent of his guests. He has bonded out since his arrest.
"The safe practice would be if you're going to have cameras on the premises like that, I think that needs to be explicitly in any sort of rental contract and I think people need to initial for that and if there is any issue about the cameras it should be removed just to protect the owner," he said.
AirBNB released a statement saying they permanently banned Natt and apologized for what happened to the guests.
If you're concerned you're being watched in a rental property, experts recommend you look for hidden cameras by using the light on your smartphone to spot a reflection from a lens.
Bottom line - if you own a short-term rental, be clear with guests about surveillance cameras and if guests don't feel comfortable they should choose to rent somewhere else.