An iPhone 5 or newer and the latest update should get you GPS without cell signal if some of you are having trouble.
Spent the last two seasons with "phone for GPS" guys. Not a fan.
I like having my laptop and GPS showing pretty much the same thing. I can copy all topo, sat imagery, geopdf, marked up roads, tracks, and waypoints over to my GPS much easier than to my phone. If I'm in a spot and take a bunch of points, I like to drop them back on the laptop that night and formulate a plan on a 15" screen and have all the extra overlay data available, and do it all without Internet.