Do you both have iPhones? Yesterday we turned on our Find My Friends apps since we both went for long, separate outings in the woods. I got home after dark and ‘Bent had been watching my route. You could even just share your Apple password and she could use Find My iPhone but then you can’t choose when to share your location.
We do, but her concern was in part how quickly my phone battery was dying in the cold. Using an inner pocket made a big difference. She’s been thinking of having me carry a tracker for a while so she can see I’m still moving and if I’ve turned home yet.
My iPhone goes to 1% battery pretty quickly in the cold unless I coddle it. It seems to be happy inside a neoprene sleeve in an inner pocket for a few hours but I wouldn't count on it for a really long excursion or in a wilderness situation.