[deanhills]

[...]

one can't jam the whole em spectrum that easily.. you need cosmic level energy for that... lol

You're so right @rudra.  Thanks for the detailed explanation about the technical workings of the jammer.  Looks as though one can end up making things worse than they are.  Like advertising one's position in reverse.  Guess the only real way in the end is to make sure one doesn't create a situation where someone is so interested in you that they want to track you.  Like try one's best not to become a target.  And as far as one can be very careful when one uses public wifi.  

I'm not an expert on the workings, but am I correct that if one is in public WiFi that an evil doer can hack into one's device if one should unwittingly use that evil doer's WiFi?  The evil doer can get one to sign up through registration by acting as though the evil doer is legitimate with very strong WiFi - and then once one has registered can get access to whatever one signs up with while using the evil doer's WiFi?