Very interesting subject....so, here is my 2 cents...
I do a lot of hunting in areas with little to no cell phone signal. When I can, I prefer to bivy hunt. With this being said, I still bring my cell phone with me.
When it comes to bivy hunting, I ALWAYS bring items which have multiple uses so I can reduce my weight. I have started to get into the habit (the past 2 years of taking my cell phone with). Here are the reasons why: (1) alarm clock, (2) camera (and video), (3) digital maps, (4) GPS, and (5) a means of communication (text/voice) on occasion. Due to the aforementioned, I have been able to reduce weight that I carry, but this has also introduced a new problem (which I will get to later in this post).
Please note that my usage of the GPS functionality with the cell phone is ONLY as a backup. I do rely on my Garmin Montana as my primary GPS. I do not feel as if the smartphone is a soley reliable means of a GPS system - yet. In the future, it will get there, but I do not think it is there yet (waypoints, bread crumbs, accuracy...).
On my cell phone, a Motorola Android Maxx, I downloaded the Backcountry Navigator Pro application. I like this application because you have great quality digital maps (topos), satellite overviews, and overlays of topo contour lines onto satellite maps. I bought the add-on, landownership. This add-on is just as good as the XHunt (name???) maps for GPSs. The only thing this add-on doesn't have is landowner information (name, etc.), but it tells you state, national forest, blm, etc. It is really good!!!
Now, for the only problem this has presented to me is to how to recharge my cell phone out in the field. I have tried solar, but have found that even in the sunny state of NM, it is not reliable. So, I have bought a Brunton Hydrogen Reactor and will be testing this out to solve my problem issues...
Hope this helps....take care.