What is the English term for those who cannot part with their smartphones anywhere or at any time?

Solution 1:

The person is smartphone dependent or a smartphone addict. The typical "addict" is a teenager or young adult, between ages ten and 30. They are numerous in all affluent countries and in some developing countries as well.

Read Smartphone dependency: a growing obsession with gadgets

Are you smartphone dependent? What a typical addict tells us about this:

"I'll admit it: I check my smartphone compulsively. And the more I use it, the more often the urge to look at it hits me. Where? In the orthodontist's office. Walking my kids to school. In meetings. Even while making breakfast. Sometimes it is in my hand before I even know what I'm searching for. Sometimes I tap the screen absent mindedly -- looking at my email, a local blogger, my calendar, and Twitter". Health & Balance

Solution 2:

In one of the linked questions, Hugo posted the following answer:

In an similar vein to idiot box, a derogatory name for someone who uses their mobile phone a lot is smartphone zombie.

As evidence, they provide Urban Dictionary a CNN story on smartphone zombies, and a Flickr collection of photos that uses the expression as its title. This article from november 2014 shows the expression is still in use by the media, although I've never heard it before.

In another related question, Manish introduces the term "nomophobia" (from no mobile), which refers to the anxiety some people experience when they don't have their mobiles. His source is wikipedia. That suggests "nomophobe" as a potential answer for your question. I also never heard this expression, although it has also recently been in media, in september 2014.

I tried google-trending the candidate expressions that seem reasonable, with little success. Below is the graph, "nomophobia" is the only term with enough hits to actually plot. The remaining terms are "smartphone addict", "smartphone dependant" and "smartphone zombie".