Ever since the popular television show "Candid Camera" was first aired, people became more aware of the possibility of hiding a camera to spy on somebody. This fascination with seeing people's unguarded moments, combined with the technological advances in video recording tools gave rise to the hidden spy cam industry. Camera manufacturers had to take into account that people wanted to have similar equipment to the type seen in spy movies and on television.
There are various reasons to hide a small camera to spy on someone, and some of the reasons are not always wholesome. Many people use such cameras to spy on their neighbor while they get dressed, and several cases of people secretly filming others having sex have caused several problems. This is not to say that hidden spy cams are always used for immoral purposes, since they have been used to great effect by the police, FBI, and other law enforcement agencies.
Some cameras that are so small as to be practically undetectable are currently in use all over the world. Some of the surveillance devices commonly seen in popular spy movies are real. For example, there are several cameras on the market that look like simple pens. Even modern cell phones with high tech cameras can be used to spy on people. The most popular place to hide spy cameras is inside common household items that include an electric cord.
Several battery operated wireless cams can be hidden anywhere. Some people have caught their spouses cheating on them or caught nannies stealing or abusing their child thanks to hidden spy cams. Even people that don't know much about technology or electronics can buy a miniature spy cam, hide it, and start monitoring in just minutes.