Car camping? Sure! RV? No problem! Live-aboard size boat? Why not?
Engine+battery means near unlimited power. If you are within range of cellular then a cellular booster on the roof (not cheap) will get you pretty good range. Basically makes 1 unreliable bar into a usable signal.
Not cheap at $600 for a Shakespeare cellular booster, but not any more than any other nice piece of technology. Less expensive than a nice laptop or tablet. Check Westmarine.com
Going a little farther with the RV or boat? HAM it up with your radio license. Packet radio is real, and useful. I have only information handed to me from others who use it, there is a lot of information available.
Hiking? Well Ham Radio sets are now quite portable. There are portable handsets that weigh less than a pound capable of packet radio.
Hiking in an area with cell signal? There are a lot of these kind of areas around. Pack some lightweight Lipo batteries, such as from model aircraft, and a power converter to USB, available for about $10. (check Hobby King USB charging adapter)
With old cell phones external high gain antennas were a real thing. Aiming a nice directional antenna at a tower on the horizon (5-10 mile away) would make a phone go from no signal to full signal as long as the aim was held. I am unsure if this type of thing exists for modern phones.
Don't discount modem over satellite phone. Yea, I wouldn't want to go there either.
So having to walk with equipment for making these calls and having internet access? I wouldn't want to though it can be done. Camping with a car, boat or RV, not a problem