Have you used Wireless dog fence?

Have any of you dog owners used this so called <a href="http://www.anrdoezrs.net/click-5691196-10853512" target="_blank">Wireless Dog Fence</a> <img src="http://www.ftjcfx.com/image-5691196-10853512" width="1" height="1" border="0"/> ?
Do you think this is necessary?
I wonder if any other animals or naughty little kids can use it too.

<a href="http://www.dpbolvw.net/click-5691196-10853508" target="_blank">
<img src="http://www.awltovhc.com/image-5691196-10853508" width="180" height="150" alt="" border="0"/></a>