A spy gadget is any device that can be use to spy on, or inconspicuously watch, while giving you the appearance you are not watching.
Some of the most popular spy gadgets for surveillance are Spy Cameras like Spy Pens and Spy Watches. Both have a tiny video recording camera of internal memory, and a microphone. All this is put on a tiny circuit board, and put in side the spy camera.
Other spy gadgets allow computer monitoring capabilities that allow you to watch the online activities of children, partners, or employees. You can see what websites are visited, emails sent, and any chat conversations.