We installed this about a year ago:
Amazon.co.uk User Recommendation
You will see that it is not currently available but the page will lead you to lots that are that operate in a similar manner with a different number of cameras, size of storage disc etc.
The cameras need 5v power - a mains adapter is supplied and are connected wirelessly to the base unit. The base unit can be connected to a TV using a VGA cable and the output can also be viewed on a laptop or smartphone. The output from the cameras is stored on a hard disc inside the base unit, newer records overwriting old ones as the disc fills up; we have a 2TB disc which stores over 3 months' records.
Night vision is very good (it automatically switches to B&W when the light is bad) but don't be tempted to point the camera through a window as the only night pictures you see is the reflection of the LEDs used to enhance the night vision.