The most convincing cameras are likely custom-made. Currently, the smallest spy UHD 4K cam in China, manufactured by MateCam company, is smaller than a pinhead.
Small enough to fit between thumb and forefinger, as well as motion detection and continuous recording when it’s charging.
With Low-Light Filters, motion detection, and more, This devices you have laying around can be revived as useful tools for home security. Get started today by downloading APP for free on iOS and Android