The first time I saw some night vision equipment, I was working in a TV sales and repairs shop. One of the bosses friends had some hardware he attached to the front of a camcorder, with which he apparently monitored the local car parks, for the stated reason of car security. I always suspected he was on the look out for a different type of activity, but there you go.
There are two main types of night sights that I have encountered, which basically boil down to passive and active. Passive equipment will attempt to magnify the light levels in a picture via circuitry, whereas an active device will use an infra-red light source (thereby avoiding visible lightwaves, which would alert the wildlife/suspicious persons/sleeping neighbours) and then convert that illumination back into an image that our human eyes can make sense of. If you want a really basic example of how that sort of thing works, pick up a digital camera (even your phone’s camera will do), and point a remote control (TV/HiFi/DVD player etc.) at it. Press one of the buttons, and watch the LEDs illuminate on your camera’s display! A good way to check if remote controls are working btw…
Anyway, check the link for a whole host of night sight equipment, as well as a lot of other optical equipment.

Other than your average military nut aficionado, who else might be interested in night vision equipment?
If you enjoy night time hunting, such equipment will greatly increase your chances of bagging an animal, similarly if you operate a civil protection scheme in your area, you will be able to see into the dark to check for any nefarious activities. Also, cinema ushers have recently been supplied with night sights to check for people recording the latest Harry Potter films! Finally, there is the most obvious use for such tools - security, be it civil police forces and armed response teams, or military.
So if you have a need, why not check out Optic Planet’s site, and see just what they have to offer you?