I mentioned it before but it bears repeating. There is a significant safety aspect directly related to knowing what is beyond your target in some cases.
It's normally impossible to know where someone might be if they are beyond your line of sight. Hitting them accidentally is a small percentage shot but it IS possible.
Your options are, every one goes into the woods, parks their behinds and STAYS PUT so we know where they are, use radios to communicate (still only an estimate of location unless you use expensive, single purpose, GPS-enabled radios), move only to and from predetermined places at predetermined times (still only an estimate), take your chances, or use GPS enabled phones that can show exact locations.
Phones are fantastic in this regard. No, not your TracPhone. You need high-end phones but the capability is impressive.
Combined with the emergency communication ability, the flashlight if my headlight dies, the camera for the kill or other cool shots and, finally, my thread LIVE! from the Stand!, I find the phone, not indispensable, but highly desirable.