Ok off work I'd keep the damn thing off. Period. If they complain you don't answer your phone explain politely that since they feel the need to track you so vigilantly on company time, you see no need to be tracked OFF company time, furthermore it'd be a waste of company resources to use a company phone outside company time.
On company time, however, I don't see the problem. Perhaps it's just me, but if they are paying you to do something, somewhere, and they have the means of finding where you are, it's well within their rights to use it. They aren't hiding it from you, since you know the phone's capabilities. I know lots of factories and office buildings with cameras that run day and night, and I don't see the difference with these phones. If you don't like it, don't take the paycheck. Kinda like OTR truckers, I'm sure most of the company rigs have GPS in them.