2 points
1 jammers either are - (in the case of mobile phones) illegal under british law - I don't know about GPS - but for the reasons you give ... (also the curfew and asbo boys) they could well be soon)
you are going to affect EVERYONE in range - not just yourself ....a black hole is just as noticeable - or unwise.
and if the publicised "advantage" of safety is anything to do with it - the police could be scrambled to your last known position
2 If you don't want the job ... just resign ... getting fired will loose much more.... don't you think that when you blink out of visibility someone will notice?
they'll send the unit for repair ... and the next ... and the next .... then they'll look at why it only happens to you ....
and I know that disciplinary cases are increasing at a fearful rate in this recession - some are looking to make examples .... it's a bad time to be conspicuous
I'm guessing you're an openreach engineer (don't answer that) - if not you'll both be in the same monitored club shortly.... more organisations than you might think are already using them ...
a simple GPS blocker ... is called a tree ... it doesn't take much to disturb the signal ... but not all day