I've just bought and installed one of these:
http://cgi.ebay.co.uk/SENTIENT-WEATH...3A1%7C294%3A50

Works really really well, the nightvision is very clear, has sound, and the recever can run upto 4 camera's!
I use my PC with this software:
http://www.zonetrigger.com/motion-detection/

to monitor 24/7 and record only when motion is detected in my specifed zone. Also need one of these to hook up to your PC:
http://cgi.ebay.co.uk/USB-VHS-TV-to-...3A1%7C294%3A50

Or just use an old VCR or direct into your TV!