The motion detector cameras are excellent hidden cameras because they use less energy. They require fewer batteries and are the most cost effective camera you can purchase. This is because they only begin recording when the sensors inside of the unit pick up movement in the room. The camera will activate when it detects movement and immediately begin recording. These types of cameras will record the video to things like SD cards or send it out via wire or wireless directly to a monitor screen or a recording device. This is commonly used for video surveillance for security guards and other job types. Some people like to put the motion detector cameras outside if they suspect someone is tampering with their car in a specific parking space and they don't know who it is.
Some of the motion detection or other hidden cameras are timed. They run for a specific amount of time that you determine. These cameras are often used in things like nanny cams and other surveillance cameras. Most people who use things like this want to verify if the babysitter is treating their children right or if the kids are out of control when you leave the house for a few hours. The timed cameras will begin recording by you turning on the device. They will record for a set amount of time and then stop. This could cause you to miss out on vital information or details.
Nanny cams and other hidden cameras come in a large variety of shapes and sizes. They are great because they usually come in a format of a stuffed animal, alarm clock, wall clock, book, or some other thing that has a hidden camera inside of it and you cannot see it no matter how hard you look. These cameras blend in well with the environment. You can purchase a hidden camera in the form of a book and place it in the bookshelf with the rest of your collection. No one would ever suspect there was a camera inside and it would not be evident.