Save your money....that's why you're taking on another job, right?
You'll find the stuff to be hot and/or uncomfortable and you'll tire of people noticing it and commenting and and once the novelty wears off, you'll toss it in the closet, money wasted.
BTW, "cheap" and "effective" don't go together. You get what you pay for.
Actually for the health benifits more than anything else.
Those were kind of my thoughts too to be honest though. Also I can't imagine not spotting trouble coming and being able to do something about it.
I promised my wife I'd ask about them though.
"Can't you at least get a bullet proof vest?"
"I'll see honey."