I resisted obtaining a smart phone until September 2015, after my third Camino. It was very useful on my fourth Camino the following spring.
The one device, an Apple iPhone 6S, replaced an "old school" flip phone, a digital camera, and a 3rd Generation iPod Touch, with requisite chargers and cables. The iPod Touch did nearly everything except make phone calls. It gave me Wi-Fi access where it was available. Each version of the iPhone comes with a better digital camera. My Canon pocket digital camera took 14 megapixel photos. The iPhone takes 12 megapixel photos and has many more features than the Canon digicam.
On a total weight carried basis, even with the Apple "piggyback" battery that gives me two full days of GPS and data use on a Camino, the iPhone weighs less (together with Euro charger and cord) than the three devices previously used. THAT makes it a wise investment.
So, unless you are a "professional" photographer taking "money shots" along a Camino, a smart phone should be more than adequate to your needs. But, for God's sake please leave the selfie stick at home... IMHO, that is one gadget too far.
A similar paradigm exists for small tablet / reader devices. While most have Wi-Fi capability and a web browser, you must be someplace with Wi-Fi internet for this to work. Between those points, the tablet is largely dead weight, unless you can find a guide book that works for you.
I actually preferred the small, old school flip-phone for voice and text use. And I used one for years, including on my first three Caminos. However, I am a convert and glad I made the shift. The contemporary smart phones are essentially information and communication "Swiss Army Knives." They have far more uses than you can likely employ on Camino.
Did I mention the built in flashlight and alarm clock, GPS, route finding, a whole library of reference books, online language translation, language dictionaries, language lessons on mp3 in the music library, and the entire world of information and knowledge at your fingertips?
The challenge is having too much information to sort through. You must also remember when to turn off messages and voice capability so the outside world does not disturb you constantly.
My favorite use for my iPhone is to make advance reservations, or change reservations using eMail and Google or Bing Translate. This helps me make my own way along a Camino. Google Translate also helps hugely when trying to find something in a shop or farmacia.
Finally, I live in the US and have t-Mobile as my service provider. My plan is called a "Simple Choice" plan. I have a 5 Gb monthly data limit and only very rarely exceed that limit. However, t-Mobile "rolls over" unused data for each month and puts it in a "Data Stash" to be used after you exceed your monthly limit in any given month. I just rolled into my Data Stash for the first time in 15 months. I had 20 Gb "banked." This was because I was using my iPhone as a "personal hotspot" to provide Wi-Fi to a notebook computer over Bluetooth. This is a very nice feature to have.
Also, t-Mobile permits me to use my data allotment in 140 countries around the world, including all of Europe. This means my Wi-Fi, data use, and text messaging is unlimited and free (subject to monthly data plan), with no roaming charges. This includes all of the Caminos in Spain and France. In fact, my signal strength was consistently BETTER across Spain, even on the Meseta, than it ever is here at home.
Finally, t-Mobile charges 20 USD cents per minute for any phone call placed anywhere (local or international) while abroad. I only used this VERY sparingly, and then because I have elder care issues with a parent back here in the States. Still, the charges after a month in Spain and Belgium were less than the cost of a Spanish SIM card.
BTW, when you are someplace with decent Wi-Fi signal strength, and you have "allow Wi-Fi calls from this phone" turned on in Settings\Phone, your international calls are FREE on t-Mobile. I just checked my monthly bill after nearly a month in Spain and Belgium this past November and December. While I did have nearly 25 USD in toll charges, all at 20 USD cents per minute, this was cheap considering the issues and need to communicate when and where I choose or need to.
I also made several LONG Face Time calls both video and audio over W-Fi, or using my data, again for free. One was placed to me while I was drive a rental car across Spain, from Madrid.
These devices are very useful. In an urgent situation, they can be a life-saver.
I hope this helps.