Andy you also need a DVR card to go with it so that the footage can be recorded to your hard drive and it doesn't sound as though it comes with a lens, only the mounting ring.
Another thing to remember also is that with a DVR card the max frame rate is shared amongst ALL the cameras so a 25fps 4 camera card will only give 6fps with 4 cameras and again beware further as sometimes you'll find resolution has an effect on frame rate also so a 25fps car might be a 10fps card at full camera resolution. You need to check the specs very carefully.
BTW there's a link to a site selling the cameras in the Youtube video.