Its not the buying, but the USEING of a cell phone w/GPS to consider. Where does it stand in your list of "Stuff" to get to improve your hunting odds? If a heaviely traveled topographical deer funnel is split by two properties [really low odds of that], and you want to hunt 30-60 yards off of the property line, well so would they. It will only take one "busted" by them for the area to turn nocturnal, at least for big bucks. DO you want to waste your time? Instead, as "they" always say, to improve your odds, scout and know your hunting area. On the flip side, quickly relocating a fishing hole on a large body of water, DOES make for a more enjoyable day. Eventually cell phones with a GPS will become common, and less expensive.
For me, in the mountains of SW Virginia, I use a map, and spent my $'s at Forestry Supply on a very good Silva compass [+ how too book] and an Oregon Scientific $50-$60 NOAA radio [fits into a shirt pocket]. Attach "ear buds" to it to quietly listen for when a changing-wind-direction front will arrive [= change stands]. Use a map's broader picture & a compass to Id & get you to a Topo-deer travel corridor. You will know it when you find it. Deer have been traveling the corridor for hundreds of years, because it is the easiest and fastest way to transverse that strech of land. Learn all this from "Mapping Trophy Bucks", and "How to Hunt in Any Weather". I get elevated with a Lone Wolf hang-on. It is the easiest to pack-in and take-down and put-up, to re-locate when a wind change [ie. thermals and fronts]. Read reviews in "Midway Gunsmith Supply". Now that I have all this "stuff" I'll consider a small, inexpensive, GPS locator just to shave a few minutes of time off of finding a stand location during astronomical twilight.
Best of luck