We find our iphones very helpful in travel.
First is the Allstays app to find campgrounds. A must have.
Then there are the weather apps. We are big hikers and its very helpful to see what 50% chance of showers means by checking current radar before hitting the trail. When the rain is 50 miles away and moving away it gives us confidence to venture further afield.
We find Apple maps/GPS to be very helpful in highway navigation. And the DW loves to check out the next Starbucks up the road.
Email keeps me in touch with my customers are lets me respond to enquiries in a timely manner. Someday when I retire this feature will be unnecessary.
Sometimes I even download free topographical maps for backcountry hiking. That way the phone's GPS shows me where I am even when there is no cell coverage. Occasionally its handy to know how far along you are on a trail or how far it is back to the trailhead.
The phone's altimeter apps are fun too. How high are we now and is that why I am panting?
Most importantly the phone's camera takes much better pictures than all the digital cameras I have owned over the years. It even puts the GPS coordinates on each image for easy cataloging, sorting, etc. My fancy Canon camera still comes along on trips, but usually stays in the Scamp
Bottomline, some of these uses need a nearby cell tower, but many do not. OTOH, I almost never make telephone calls.
We do carry a cell signal booster with a roof mounted antenna that can turn one signal bar into three. Its helpful, but not a miracle worker.
Occasionally we even tether our laptop to a phone for connectivity when longer typing sessions are needed. I also carry a bluetooth keyboard for the phones, but usually forget to use it.
We are on AT&T and find it usually works well.
PS. Image below is from Grand Teton National Park last week.