Spy cameras are tiny pinhole cameras that have been concealed in everyday items, allowing for discreet monitoring. They are commonly used for home recording – both in the event of something like a burglary, and then also for childcare (and even elderly) monitoring.
Wireless cameras are a popular choice, as they allow for the camera to wirelessly transmit its signal to the recording device, rather than having to run (and conceal) any video wires.