It may be that this gps thing is quite common, but if it's escalating to carrying other things like torches, "...just in case."
These are safety behaviours, and they're actually pretty normal and healthy. Wearing a seatbelt? Keeps me safer, doesn't cause me any impairment or distress & all cars have em - so great, seatbelt it is.
The danger with safety behaviours is if they snowball out of control. What may have started with casually tossing a gps and torch in your handbag, "just in case", quickly becoming "must not leave the house without the gps and torch and, and, and...", or worse still, "It's safer to just not leave the house at all."
Have you talked to him about how he uses the gps? Does he check as a matter of course where you are every hour, or just when you're late home or something? Is it going to cause distress to him (or you) if, for any reason, either of you were to go out without the gps tracker?
In my mind, it's not so much the presence of the gps tracker that's a problem (we do odd things to accommodate our ptsd sometimes, and that's ok), but rather, how it's being used and whether it's helping (or exacerbating) his (and even your own) anxiety.
Keep in mind that you'll adjust to these safety behaviours as well, and it could easily become the case that whereas you were ok before, you become panicked about having to leave the house without the gps (& torch, and...) as well. That's not healthy, that's regression.