I have a radar detector. Not a super expensive one... but I'll tell you what it does help with... When your detector doesn't go off and you get pulled over... the cop comes up to you asking you how fast you were going and saying you were speeding... You know he didn't catch you and you say, "I wasn't speeding", and he starts huffing and puffing and comes back and says "you're lucky I'm deciding to be nice tonight", yeah, sure bud... bye.
I don't completely agree with the fact that they are useless to the point where you're already getting a ticket when it goes off, mine goes off before I see cops most of the time.
If you're really worried about it, google scramblers. I do not condone this type of equipment... lol or do I?