One US couple found such a surprise while staying at an Airbnb in Florida, reported ABC Action News, Tampa Bay. To the untrained eye the master bedroom had what looked like your average smoke detector. However this one was above average, and luckily the occupant worked in tech and realised things weren't quite as they seemed.
What was discovered was a hole in the smoke detector containing a camera that was pointing right at their bed.
This story does have a happy ending. The couple called the police, an SD card was found containing images of a few different couples and the home owner was charged. He was also banned from Airbnb although he'd been with the site for two years before the shocking disovery.
Police have put out requests for anyone who'd rented the room from the man, or had even just visited him, to contact them.