This is an application I have never had to make use of, but if I lived in an area where I could do something like this, it sure looks like a lot of fun. There appear to be many different ways to do this - and many of them very affordable. Ultimately, I think a lot depends on how much you want to spend and how serious the project is. I found some interesting websites:

The High End
http://www.pixcontroller.com/products.htm

http://www.hunting-cams.com/c-11-wireless-cameras.aspx

Here is what is being used on the website that you referenced:
http://www.amazon.com/s/?ie=UTF8&key...sl_10ro1gi961_b

The trick seems to be power supply. Have you tried to reached out to Simon King directly?

James