For very little in cost, time and knowledge one can build a short range GPS jammer that will block the GPS signal from getting to the phone.
What you want will only track honest people who, as a rule, don't blow things up.
84 posted on 08/11/2006 4:07:10 PM PDT by RFC_Gal
(It's not just a boulder; It's a rock! A ro-o-ock. The pioneers used to ride these babies for miles!)