Phone Jammers

has any one here every used a phone jammer?
you can get them of ebay now for about £50.they knock out all mobiles within 30ft'ish.if you can buy them for £50 and go for 30ft...... i wonder how big the ones the goverment have and how far there's can go?

[edit on 30-5-2008 by rikgrimsby]

Mod Edit: All Caps – Please Review This Link.

[edit on 30/5/2008 by Mirthful Me]