Truthfully, you may be better off ordering a fanny pack, as unfashionable as they are. That way, you will have all your stuff available to you even if you get separated from your horse.
I live in an area where I really don't need a compass, GPS, etc (thankfully), but if I lived in a woodsy area where long distance visibility was nonexistent, I would have them. As it is now, I am riding trails that I've ridden for 25 years and if I do somehow get turned around, all I have to do is ride to the top of a hill and I can see everything in the surrounding 10 miles to get my bearings.
Cell phones rarely get a signal in my area, but I take it with me anyway, and I usually let someone know where I'm going and when I plan to be back.